Hi gruffy, I haven't come across any new AGs in UK shops recently but I've just recieved a disc copy of Black Mirror 2 in DVD box from
Interact (link at the top of the page) Interact are based in the US but I've ordered lots of games from them over the last few years, they are very reliable & I usually get them within 4 - 8 days!
N.B. Unless it has become available during the last week I didn't see it on Play.com or Amazon UK.