I have actually run out of R12, as some of the walkins that I work on run with R12. I'd like to make you an offer but due to the UK/US customs and the restriction of virgin use of R12, I don't think pressurised gas would even get out of the US let alone into the UK without expensive documentation and all the other billy hoo.
I still have 5 or 6 hundred pounds of it taking up room in my shed. I'm just waiting it will come back in style some day. Like bell bottom pants, tie dye shirts, and government protest. Trust me it's on it's way.