Do you buy btc for cash? or is it only other payment processors?
Am I working it right that taking current market of mtgox as 29.8, you would buy for 29.8*.96 = 28.608 and converted to GBP via xe.com taking current rate of 1 USD = 0.609669 GBP would make it 1btc = 17.4418 GBP

If so, I will probably have some BTC coming your way once my mining rig arrives