Thanks for your replies everyone. I do plan to use ATMs extensively in the UK while there -- just wanted to have some GBPs beforehand as walking around money *just in case*. On the subject of ATMs, I remember vaguely reading about problems some travellers have when using ATMs abroad; from what I remember, the problem had something to do with PINs having 4 digits rather than 6, or vice versa. Does this ring a bell with anyone?