Thanks for all the advice guys. Just to keep you up to speed, the ZKB were very helpful, giving us a print-out of where the money went. The money was indeed lost through exchange rate fluctuations. They obtained all this information from Natwest, who had denied all knowledge!!

Most interestingly, they informed us that Natwest had given us an IBAN that was only valid for Euros. I am absolutely spitting! Essentially this means that any transactions I have made to the VISA card have gone CHF -> Euro -> GBP. Any suggestions on how to deal with Natwest over this? There must be a way to get some compensation for this incompetence.

Others might want to check that this is not also happening to them..

Cheers

Jim