Hi,
Called into a local garage today that used to be a franchised Vx dealer many years ago and asked their advice.
They said that in their experience the EHPS is a plug an play and that they were not aware of any need for reprogramming.
So armed with that info I bought a replacement from a local scrappie that came off a diesel 54 plate no idea what the mileage was but really I wanted to prove the theory and the practice of the change.
Swapped over quite easily once I realised I needed to swap the carriers ... mine was slightly different shape.
Followed the bleeding instructions found in Haynes manual and it's now working like a dream.
Have cleared all the fault codes and so far none have returned and no light on the dashboard will scan again later in the week.
So my problem is solved at the moment.
Thanks for all the help.