well it's kind of like Giorgio says really, a few people have spoken about doing group buys and what not but nothing has ever really happened. Yoof used to be able to get them from Germany, although it was mainly mk1 and 2 panels but I think his supplier has disappeared now anyway.
There are plenty of fibreglass companies in the UK who could make panels (google search it) but it's not economically viable unless you can get about 10 people all wanting the same things.