Hi. I took the car back to my garage with the information you provided. They had reset the learned values when the DPF filter was changed. Interrogating the ECU today revealed that the engine had tried, unsuccessfully, to regenerate the DPF five times since the filter was changed. They spoke to the Ford Technical Department which was very helpful. Further tests including a smoke test on the engine, revealed that a rigid plastic pipe at the rear of the engine (forgot the name) had two holes in it. This pipe was replaced and further tests done. The ECU was still trying to initiate a regeneration cycle, which wasn't completing. They replaced the DPF sensor with a new one and forced a regeneration, which completed successfully. Everything is now how it should be.
Thanks. It was the Ford Technical Department that explained the tests using a multimeter and vacuum tester. The original DP sensor failed that test.