Anything under £30 or so (Not sure of exact figure), including postage costs, attracts no duty. Above that, it's 5% import duty +17.5% VAT+"handling fee"of about £10-15. You might get lucky and pay nothing, or you might have Fedex deliver it, in which case they will think of a number and double it. You will get a refund after, IF you are persistant. I think they assume mosty people won't bother chasing them for £20-30, and they are probably right.