What is UK film is a genuine hidden gem?

For me, it is probably The Debt Collector (1999) with Billy Connolly and Ken Stott. Connolly plays a former heavy who has been embraced by the avant-garde art word and has tried to put his particularly nasty crimes behind him.

Stott meanwhile is the cop who originally busted him and has fallen into obscurity as well as caring for his ailing mum. Seeing Connolly being freed and entering middle class life proves too much and the two engage in a series of mind games and escalating violence.

It is head and shoulders above most UK crime films and is set in beautiful Edinburgh to top it off.