Have you seen this? www.runnersworld.co.uk/news/article.asp?UAN=481
Many years ago I had my feet measured by a machine in Sweatshop after getting loads of blisters, it worked. Not sure that they still do that, no mention of it on their site that I can see and no shops in Wales. Think experts can tell from your shoes how you run so if you visit a shop take your old shoes with you.