Bigchap

I realized you were in the UK and I in the USA but I thought, I love a good challenge. I'll google this and help find the part for you. I was floored to get only three hits on google. And two of those in a forgeing language! All I can find is the manufacture's web site:

http://www.truturn.com/cgi-bin/store...exact_match=on

I've not shipped to the UK but I would have to guess that the postage alone would make this cost more than you want to pay for it.

Sorry I couldn't help
Mike