Thank you both for your comments... and i can assure you that living in the West Midlands, i am well aware of the potential for crime and theft, and it is something i've already given a lot of thought to...
However, i don't walk the streets of Coventry paranoid about crime and letting it affect what i want to do (although people could well be forgiven for doing so), and so i don't intend to in the Lakes either.
I'd prefer to rely on the fact that if i lock a bike securely, in view, around the environs of a fell race, there are enough decent people about that i'm unlikely to encounter too many issues. I'd imagine there aren't too many people hanging around fell races with angle-grinders and the like.
Of course, it will be insured should the worst happen, and if i do encounter issues then i will have to re-think things.... and of course i'll report it on here and you can tell me "i told you so....!"