Try & get them to open a Nationwide flexaccount & apply for a debit card. It'll save them a heck of a lot of money every time they venture abroad in the future.
I agree with Colwyn. The only place I'd even consider using is USA - where they can be used the same as cash & I'd only buy to take to US if the exchange rate I was offered when buying was really, really good. (As it is now). If we were going to US later on this year I'd be tempted to buy dollar travellers cheques now.