Depends on the amount involved, but for amounts of up to £300 a day you could use a Nationwide Flex Account, card use via ATM is free as is debit card use overseas.
http://www.nationwide.co.uk/current_account/default.htm?source=ggl&campaign=FLX200512001&keyword=nationwide+flex+accountCheck out Important Information after clicking on the Current Account - more info link on the above. If you are no longer a UK resident, maybe get a trusted friend or relative or teforumer (!!!) to open the account and give you the card and PIN.
For larger amounts the IBAN situation described above is probably best. Banking with First Direct for example a SWIFT transfer costs £21 so for sums above roughly £700 it is more cost effective than cards which charge around 2.75% plus stuffing you on exchange rate charges.
Hope this helps.