Update; I had a good look underneath again yesterday and noticed a teeny weeny bit of brake fluid on the bleed nipple of one of the rear calipers. I bled it and tightened the nipple up a bit tighter than it had been and it now seems OK. Although there is still a fair bit of travel on the pedal it's not as bad as it was, the brakes seem to be far better and the pedal no longer creeps to the floor if you hold your foot on the brake. Fingers crossed that the problem is solved and thanks for all the help guys.
