There's also a nice little fabric shop in Wisbech (pron Wisbeach) which is closer, less than an hour's drive from Lakenheath. The owner there is very friendly and helpful - I've only popped in once on our way back from Norfolk, but would definitely go back again.
http://www.topstitchfabrics.co.uk
Wrt Ricky Timms Stable Stuff, yes I do own ASding, I will investigate getting it on the roll, I didn't realise we had that option. Thanks Margo, as usual, top tip