I would expect this to be difficult. Back when iTMS was US-only, everyone was trying to figure out a way that they could download from it. I know that some people were able to do so because they happened to have US credit cards I believe. As I recall, they still had to make up an address.
One possibility that may work is to see if the prepaid cards are sold in the UK. Maybe if you had one of those and you used a less than true address it would work? Since they don't have the CC info to verify your address this might be a loophole. If that is the case, then it would also seem that maybe you could just buy yourself a gift certificate and redeem it from your second identity. Don't know how the currency conversion would be handled, though.