Spoke to Bob last night who did the maps for my car he said that the o2 should not be throwing up a fault as the rear o2 sensor hsa the values really high so should not throw up any error codes, so might unplug and see if that works.
Also he said the car has two maps on and the way I can switch between them is to have ign on foot to the floor press the heated rear window button then release my foot then turn the rear window off and aprently he said that switches between the two maps one is at 1.1 bar and one at 1.3 bar
i never knew that