Dollar exchange rate - help

With slight fear of going against your rakeback affiliate code on my first post, I need some advice. I play on Carribean Sun as I like the cryptologic players and the rakeback, but have since discovered that the cost of exchanging money from dollars onto my Credit Card in pounds has cut my profits my about 70%. I need a site that I can hold my accounts in GBP and preferrably one that I get get rakeback on too. Any advice please?