Just thought I'd provide an update on this post.
I managed to find another micro sd card on eBay (the latest version) for £60 and this time it worked fine - result.
I didn't receive a response to my email complaint so phoned the dealer over the weekend and, after a bit of toing and froing, they've now agreed to reimburse the money I spent on the card - double result.
Thank you to everyone who contributed to this thread, it was very much appreciated.