Thanks for all the advice. I looked at www.moneysavingexpert.com as advised by MAN Pax (I recommend all who use their debit cards to get cash abroad to check if their card features in the 'cards from hell spot'). There is a currency exchange calculator on the site which tells you who in the UK has the best deal, I went up to Victoria Street (SW1) this morning and exchanged £450 for $886 at Thomas Exchange Global. I will take the other £50 in cash as backup.