Quick update.
Got an e-mail response very quickly asking me to call in to arrange an RMA. Rang the number on the website for non-US customers and spent 20-25 mins on hold. When I finally got through I explained the problem, gave them my mobile number and confirmed my details (had already registered them earlier that day through the website). I was then told I'd get an RMA e-mail and to just follow the instructions and that was that.
E-mail arrived containing a link to a web form where I had to enter my mobile number. After a few false starts with it not recognising it my g/f suggested removing the first 0 and that worked. I then got a 3 page form to print out and use to send the card to BFG Europe in Wales, 1 to put in the box, 1 to put on the box and 1 to keep. Will be posting it via special delivery today.
Slightly peeved that I've already spent at least £5 calling the USA, especially as the actual talking to someone part took about 2 minutes, but at least I've got an RMA!