No matter how you want to look at it, if I take a long gbp/usd transaction i am paying 1.25%(annulized) more in interest expenses than it cost you to swap that transaction. This is base on 100,000 gbp. .25 is taken off the gbp int and 1% is added to the usd. This is very expensive. It is way cheaper do deal in futures for all amounts than to take any overnight position with IB. No matter if it is 125k euro or 2m euro.