Thanks for you reply. Yeah i think what you are saying makes a lot of sense. I tried to remove the dpf but i failed, its easy enough to access but the bolts are very badly rusted and a wire brush is not helping, i cant get the tools to fit properly because of the rust, there is 2 flanges fitted either side of the dpf and they have 4 bolts each and these have a nut which needs a spanner on it too, the first bolt broke and it was one of the easy to access ones, i think they need a grinder or a power tool to remove them, my car gets parked in a residential car park and getting any power tools there is not really possible. Im now thinking i will have to pay to get the dpf removed and cleaned.Your back pressure sounds way too high and this was probably made worse by your recent issues with other sensors
causing imbalance in exhaust emissions.
If you can successfully clean the dpf then hopefully it will regenerate ok now youve sorted the original faults.