Hi Jonny,
We made our own sail last year, about 52squM with a lot of help from Arne and his design. actually we had to get the sewing done for us, in my shed, as the machine we bought second-hand for the job was not up to it. I can recommend diy sails if you have any spare time. I didn't, and i don't, so the process was not as smooth as I'd have liked, but not only did we save quite a bit of cash, but the thinking brought us a lot closer to this thing that we were new to, namely sailing a junk rigged boat!
Sorry you heard nothing from the UK sailmaker. However I know that Sebastian will build a lovely sail, and I notice that Arne is recommending someone much closer to (your) home I think? I too can highly recommend a cambered sail.
Good luck with your thinking it all out! It would be interesting to hear a rough "per square metre" price quoted if you have a moment.
Pol.
ps the previously named (Westaway?) has got a web presence, if you Google him.