Hello
Just an update.

Well, I've finally heard (by telephone message) that my contract has been cancelled. I've asked for this to be put in writing but no joy so far.
I had to send them a number of letters, and copies of my contract twice. I also sent them a letter notifying them of my intention to pursue the matter in the Small Claims Court. I gave them a date by which to resolve the matter.
The claims I was intending to make were breach of contract or voidable contract, misrepresentation, and possibly fraud (my contract appears to have been altered after I signed it). They never sent me a copy despite my asking for it several times.
The advice I would give is 1. don't give in if you know you're right 2. use the internet to get initial legal advice to support your case 3. keep a log of any contact you have with FF and copies of any correspondence 4. inform Trading Standards.
And for anyone thinking of joining FF, don't! There are plenty of good gyms around.