When they changed the DPF they may have damaged one the the sensors that reads the pressure differential.

Which would cause the car to be permanetly on regen. Get the sensors checked.

Could i suggest you go nowhere near a main dealer fit-new-parts-till-we-happen-upon-the-fault centre, you are more likely to have the fault diagnosed correctly and repaired economically if you find (preferably by recommendation) a professional Diesel workshops.

If you don't know of one in your locality ask around mini cab owners where they take their cars, they usually know where to go.

Update on this; the fault code P2458-61 ("dpf regeneration duration") is stuck in the engine PCM! The engine repeatedly tries to regenerate the dpf (hence the increasing oil level - diesel contamination from the regeneration cycle). All the sensors have been checked. The eloys liquid level was checked and that’s fine. The dpf has been replaced and the sensor voltage checked; all good. Ford dealer uninstalled and reinstalled the PCM but to no avail, this fault is ever present.

It doesn't show as an engine malfunction alarm on the dash, but I can see this when using the Forscan tool. I monitored the cycle on Forscan while driving, and could see the exhaust temperature reach 550degC, "distance since last regen" increases for approx 10 minutes, but then the cycle resets itself and starts over again. Going by the dpf sensor pressure it doesn't even need regeneration.

Beginning to think the PCM itself is faulty, or something simple like faulty glow plugs/glow plug relay..but there are no other fault codes showing.

Any advice on this would be appreciated.