Natwest charge ?18.00.
CAM similar I think so around ?30.00 all in.
Should only take you a few minutes to ring your bank or check there web page re charges though.
There isn`t a cheap way to do it, all the Banks charge similar rates and there higher if the transfer is a one off or not a lot of money.
If it`s a big amount, over ?100,000.00 speak to your financial advisor, they`ll forward you contact info for specialist companies that will optimise the exchange rate and give you a special friends rate.
If you need it quick western Union do it instantly, for a charge which is dependant on the amount, its not cheap, but quick.