Just thought i'd update this topic for anyone who drops by......
I took the decision to send my card back to the UK retailer I bought it from. After a week they too confirmed the fault and sent it to XFX. They said it could be up to 28 days to get a resolution!
Low and behold on day 28 the retailer contacted me to say XFX had given them a credit for the faulty card. They were going to send me a XFX R9 270X as a replacement but I managed to persuade them to send me an MSI one instead.
Overall i'm very happy with the outcome, if I had the spare cash i'd have probably upgraded to an 280x, but I dont