Throughout the movie, notice how despite his joviality and friendliness, Frank Butterman always somehow manages to stick Angel with any demeaning, tedious and shitty job just guaranteed to tick him off, while the other officers get the easy stuff, the day off to enjoy the fete, ice cream, etc. In light of Frank's role as one of the NWA ringleaders, it's actually a clever ploy; he not only dulls the other officers' instincts and makes them resent Nick when he actually makes them do some work, he isolates Nick from the other officers, increases his resentment of and annoyance with them and either dulls his instincts or drives him out of his mind with boredom, thus making him seem increasingly irrational and diminishing his credibility. He also ensures that Nick will get so sick of the job that it would be entirely credible if he just upped and 'disappeared' one day.
Where did the NWA got all their guns and ammunition from? American viewers might be unaware that it's actually quite difficult for people in the UK to get hold of the sort of weapons the NWA are armed with. With the exception of an occasional handgun or shotgun, all the weapons are pretty old, many of Second World War vintage. Even the FN rifle that Nick Angel uses for all too brief a time has been out of British Army service for about 30 years. They were collected during firearms amnesties, of which there have been several in the UK during recent years. Such amnesties usually scoop up quantities of wartime souvenirs as well as a small amount of unlicensed modern weapons. Although they are then meant to be melted down for scrap, this is clearly not what was happening in Sandford. Instead, with the connivance of the Chief Inspector, the choicest items were being siphoned off and handed out to the NWA's members, with a strategic reserve being stored in Arthur Webley's barn. Even better, the timeline puts this as having happened for about twenty years at the time of the movie, which means that when the NWA started their crusade it was before the real crackdown on firearms in the UK (the two main laws of which were passed in 1988 and 1997) When every other police force got tough on guns, the NWA just stockpiled them. No wonder they can get hold of the types of guns they have.
Angel only starts chewing on the toothpick in the evidence locker for one reason: to spit out in the the town square. The town, obsessed with neatness as it is, now has a little tiny piece of litter laying on the ground, just another part of Angel's giant 'Fuck You!' to the NWA.
At the end, the first officer to believe him is Walker (Oi r'ck'n e's gut summat thar). We know that Sandford has been living the lie for approximately twenty years, at least since Danny was a young child. Since most of the officers on the force are about Danny's age, they would have been children when the NWA first started as well. Walker is the only one who is older, and is definitely old enough to remember a time before the NWA were in charge, and thus the most likely to be able to realise that Angel might be telling the truth.
Nick recruiting the kids to spraypaint the cameras. At first it seems like he's just getting them with the promise of mischief. But considering the towns obsession with being perfect, the kids must have been really prevented from being able to do anything that would disrupt it's image. And whats more, the NWA has shown it will kill minors who might lessen the towns chances of wining the contest. The kids were acting with Nick in self defense! This ties in to an abandoned sideplot. Originally the leader of the hoodies was revealed to be the grandson of Weaver, the man behind the cameras. Nick would discover this but wouldn't reveal it to Weaver, gaining the hoodies trust. Another bonus: the boy would've been called Gabriel, after one of the archangels.
Why couldn't the NWA members hit Angel? Well, okay, he got hit twice - once after exposing himself from cover and then with sleeve guns - but even then relatively close range from handguns. The NWA had never used their guns before - they couldn't. It would be one thing to practice with them - loud as they are, the countryside around Sandford is big enough to minimize that - but their ammo is probably limited (see above explanation about firearms in the UK). It's also harder to make an 'accident' out of a fatal gunshot wound, a high 'suicide' rate would reflect very badly on Sandford, and the noise doesn't fit with their behind-the-scenes M.O. In short, Possession Implies Mastery is being subverted here. At the same time, Frank is the only NWA member to accurately hit anything of a smaller size category than "the broadside of a barn" (the chandelier at the pub - without looking, either!). He's probably the only one with any kind of firearms training at all. Then there's the cops - sorry, 'police constables' - but that's probably just suppressive fire (warning fire, with the trolley boys) as much as anything. We only ever see them shooting at the vastly underarmed supermarket staff, so there's less justification for them to shoot to kill. That, and they certainly know everyone involved.
The reason the other officers are so good at armed response? Frank's been setting their training so that, with their skillsets, there's no way for them to transfer or be replaced. Thus, their actual aptitude in standard police work is kept to such a level that they're only useful as pawns under his control, keeping any other station from wanting them besides the obvious benefit to the NWA. And as the outside chance that they would ever leave Sandford is reduced, the chance that any replacements would come in from outside is also low, as what training they do have also makes them hard to replace. Ex: from what we can see of him, Sgt. Fisher might be described on paper as "highly trained in SWAT tactics and media relations" - who could replace that, and then all the way out in Gloucestershire? More obviously, that lack of standard policing knowledge also keeps them from believing Angel (or any officer not raised under Frank) for far too long, and ensures an impressive level of frustration for the newbie.
Sgt. Popwell actually had his breakdown, and was then killed for the petty reason of being a public nuisance, not because he discovered anything sinister. The other officers don't talk about him, for one - you'd think the Andies at least would call Angel the 'replacement' or something - and even they would at least be a little suspicious if he disappeared for no reason.
When Angel sees the action movies at the gas station, he's not thinking "I'm Nicholas f*cking Angel, and I need to go back to Sandford and be Nicholas. F*cking. Angel!" - he's thinking "...Danny!" - that's why he looks so pissed, and why he can't waste time bringing back the full brunt of the MPS. ...which he could do - disgraced as he is, London has absolutely no reason whatsoever to think he's a liar. Even if Danny did something like claim that he destroyed his car to make Angel's death look kinda real, the NWA would eventually catch on (where's the wreckage?), and then he'd be a dead man. It's probably part of why he looks so down in his patrol car just before the shootout; as well as the shock of the masquerade being lifted, a movie buff like him wouldn't miss the fact that his dad and the people he grew up with are going to 'accident' him away in the near future. That then becomes "Nicholas f*cking Angel is back!", and then "I'm gonna clean up my hometown! *pump-action cock*"
When breaking up with Janine at the beginning of the film, Angel mentions "guilty people often make the first move". It seems to be a throwaway line at first, but the "guilty" people of Sandford (i.e. those working for the Greater Good) all initiate conversation first when meet Angel, thus making the first move themselves.
One of the Andies says "People have accidents all the time". He has grown up in Sandford and actually believes that the accident rate is completely normal.
Okay, murdering everyone who's a nuisance to the town is a fairly obvious way of telling that Sandford's residents are very much keen on staying clean and pure but taking a look at the names of the members of the NWA can also net you a hint. Shooter, Treacher, Skinner, Weaver. These are all last names that originate from the time where last names started to become popular and getting a last name based on your profession was fairly common.
PC Walker may seem like just a dirty old man at first, throwing out dirty words every now and then, like "Tits." and "Cocks." Then you realise, he is actually giving one-word explanations of Doris' hideously bad double entendres.
Frank Butterman never once outright lies about the murder-rate in Sanford. Every time murder is brought up he says "There hasn't been a recorded murder in over twenty years.". There were murders, dozens most likely, but the were never reported/recorded as such.
Near the end, where the naval mine blows up. Think about it. The whole movie is filled with Chekhov's Guns, one of which is the naval mine. This Chekhov's Gun was in the evidence room, which was, in effect, an armoury. See what they did there? There's a Chekhov's Gun in an armoury. Considering that the armoury itself is a Chekhov's Gun, it's a Chekhov's Gun in a Chekhov's Armoury.
We constantly see Angel with a radio over his right shoulder. So why, when he went to buy Danny a rubber plant (Japanese Peace Lily,) why didn't he use that one, from inside the store? Because that was the one time in his life when he was out in Police garb but not in regulation vest and equipment, because he simply grabbed his jacket at the station and legged it to go buy Danny a gift!
Fridge Brilliance: When Angel turns away from the florist's counter to go and use the radio in his cruiser, the robed, hooded NWA member behind him would have been in plain sight to Leslie Tiller. Why didn't she scream, or try to defend herself? Because she was one of them! She thought the hooded member was there to give her the call to action, or perhaps to wish her farewell on her trip.
Fridge Horror: The underage drinkers that Nicholas arrests at the beginning later show up dead at the hands of the NWA. Without realizing it, Nicholas accidentally sent them to their deaths.
It is possible that Martin Blower was killed in what appeared to be an appropriate way - a car crash - not because he was an appalling actor, but because Angel caught him doing about 45 in a 30 zone.