I do the same, a few euros to get by and then cash card. Nationwide accounts dont charge for using their card abroad, so your only charge is from the spanish bank, which is £2 at most. Most UK banks charge for using their card abroad, usually around 4-5% of the transaction, limited at around £4. So this including the spoanish bank charge will cost you around £6-7 per withdrawal. Seems a lot but put into context, if you make 3 or 4 large withdrawals it'll cost you ~£20, when you'd pay loads more commision on travellers cheques. I set up a nationwide account just for this purpose.