Never been 'stung' by Barclays, and always use the ATM at a reputable bank abroad, so don't get hit with ATM charges.
At the end of the day, is all this shopping around to save £10-£20 really worth it, especially if you take more money than you need for the holiday, and then spend it on useless crap, or have to change it back again in the UK and make a loss on it?