That's not how I remember the Caxton Global card working, you load it in Sterling and then get the exchange rate minus x points whenever you use it, it may have changed in the last couple of years though. I've got their Euro card as well and found them very easy to deal with and never had any problems with them being accepted although I was never very far off the beaten track. Things to remember are that you shouldn't use them for deposits on hire cars or hotels as they reserve (shadow) part of your available balance and you can't use them at toll booths or car parks as they need a connection back to base to see if you have a big enough balance, I suppose that means they won't work in the back of beyond either if there's no data connection.