When David loses his job and Neil offers it to Tim, he recommends Gareth. They've always had an antagonistic relationship, so seeing Tim doing something nice for Gareth reminds the audience why he's the bigger man in the end.
In the finale of the UK version, when Chris makes fun of David's girlfriend and David tells him to fuck off.
"Never give up."
After David stood up to Finchy and before Tim got with Dawn, we see both David and Tim hanging out with Gareth. Three men who have always rubbed each other the wrong way have decided to make the most of their respective situations and try being friends.