For Uk residents - the Halifax "Clarity" credit card is good for that purpose - no charges / penalties and you don't need to pre-load it - just pay the bill at the end of the month and they give you the exchange rate of the day. Very easy and straightforward and since it's a credit card you get the benefit of credit card purchase protection too. (It's also good for any foreign currency purchases on the internet).
Other travel tip - If you're a UK driving licence holder, always have a couple of pre-prepared Licence Verification Codes printed out and shoved in your Nav-case. You never know when you might need a hire car and you can't always guarantee you'll be able to get on-line at the rental office. (The codes are valid for 21 days).
OH