It was a conversation in the comments for Steve G's review of Legend that inspired this list. Basically it's a list of films, TV movies and miniseries to feature queer characters (either explicitly or implicitly) in the genre of British gangster drama. I've also included some examples of homosexuality in prison drama; the original banned PfT version of Scum (the subsequent film adaptation removes Carlin's sexual/power relationship with a fellow inmate), Ghosted and Starred Up. This tradition obviously stretches back to Ronnie Kray's homosexuality; as such you'll see a few films based on the Kray twins as well as films with characters clearly influenced by them.
I'm sure there's more than these listed here so I am open to suggestions. Narrative films only please, no documentaries.