Call me stupid... but what's wrong with using a standard cash card or credit card? I always have in the past, it seems to give me the best rates even after the fees..
Some cards do, some cards are awful and load the exchange rate or add fees.
Not everybody has access to the best cards (Halifax Clarity, Nationwide Select).
Try using your standard HSBC or Natwest debit card abroad and work out how much you've been charged (either fees or rate loading).