Account/ currency advice please

hi there

iv decided to fund a live account some time in the future! the currency of my country is the euro and was wondering because i trade gbpusd would it be better to fund my account with sterling ? my thinking was (please correct me if im wrong) everytime id make a buy order with my euro account of gbpusd an exchange rate of euro to sterling is made? what i mean is rather than the euro account making numberous exchanges to buy gbpusd (which could mean i would be loosing money if the euro was weak to the pound), wouldnt it be better to just change the account to sterling? and get the best exchange for my euro in one transaction? (please correct me if im wrong on this)

regards

mike