If you get in contact with your region's windows phone evangelist, they might be able to hook you up with a free app hub subscription. In Australia I believe that guy is Dave Glover (
@dglover) but I have no idea about the UK.
If you happen to know someone who already has a membership they could possibly unlock your phone for you (assuming it doesn't breach any membership terms or conditions). I'm pretty sure each membership allows you to unlock up to 3 phones but they would need to physically connect your phone to a PC to unlock it.