OH GEEZ, these are hard. I know almost nothing about Coupling UK, except that it is one of those shows about a set of adult friends and their relationships, but I also think it's... edgy isn't the right word, but I think the tone is very different than, say, "Friends". I also think I would enjoy it a lot if I got around to watching it.

In Queer as Folk, Brian and Justin are really pretty (um, according to me, not what I've heard) and also in love. Brian is kind of a ~bad boy~ type. There's some interesting exploration of homophobia. Which I guess is par the course for a well-written show about gay men. I also think of this show as something you in particular hold very close to your heart, but... I guess that isn't really part of a summary.

I haven't heard anything about Billable Hours at all. But Merlin! Um, it's one of those Brit shows about the past (I say "one of those", but I think the only other current one is "Robin Hood"). It is pretty obviously based on Arthurian legend, and pretty much everyone loves Arthur/Merlin. The Guinevere character is some kind of servant in the castle, though, which has caused some kerfuffle in the fandom. Aaaaand there's Morgana.

You should!!!