Stripped off the DPF and removed the filter from the turbo oil feed - pleasgingly it was nice and clean, although the car has done 83k. There is a little play in the turbo so hopefully this will prolong its life. The engine undertray is missing, and this has led to the clamp bolt on the DPF outlet seizing - no way it was coming off so had to slice it with the angle grinder. Had a spare in the garage fortunately
Bottom DPF sensor pipe appears to be seized in the union as well - the union turned a bit but then went tight. Had to disconnect the other end to get it out. Found what I presume is the reason for the AC not working - there is a big dent in the condenser, so I assume it has split. I bought a gauge and some gas the other day, and it has no pressure in it, but as soon as I took the cap off the port, I could see evidence of dye, so it was known about - have ordered a black light, hopeful it will come tomorrow so I can confirm that is the source of the leak.