I use my debit card in ATM's for the bulk of my cash needs, and I always take some GBP cash which I change at the money changers over there, the rates only about 1php lower than the official exchange rate. If you use a debit card, you need to take into account your bank might charge you a couple of quid everytime you use an ATM, so it's better to withdraw a larger sum rather than a tenners worth of peso's.
