I also been waiting 3 months or so. Sure it's only £15 but to attract customers into buying their products and failing to fulfill the cashback claims is a quite shoddy move if you ask me.
No acknowledgment or contact whether the claim is invalid etc is quite rubbish.
I think I'll give them a ring tomorrow as they don't seem to respond to emails too!
Finally got mine!
Agree, does not seem like its a very well organised process.
I predict you'll be told that your cheque is in this week's list.
The seem to send them out every Friday, you may just get your's sent out if you call early enough tomorrow. My cheque arrived on the Wednesday, the week after I phoned (about 3 months after I made the claim).