I mentioned once on FADU that I use it but had heard it was hard to find in the UK, and several people replied telling me where they got it. I don't remember now, but apparently it is available in the UK. I can check FADU and see if I can find that thread.
AG Photographic carries it but says they are waiting for fresh stock:
That price is about double what I pay for it, though. At current exchange rates 19.95 GBP is $30.60 USD and I pay $15.99/gallon for the powder from Freestyle. However I have to admit that I like it enough I'd still use it if it were $30.