Hello guys, thanks for your response, apologies for the slow reply.
Doc78, yes my code reader will read basic codes on any vehicle with a 16 cavity DLC, it's an Autolink AL319 by Autel OBD11 and CAN code reader. Good for reading basic codes but will not offer lower link manufacturer info, hence the P0500 reading I had in the pending code section indicating ABS speed sensors. An OBD111 tool will tell you which sensor is giving trouble.
I had read the link you gave to similar problems, very good info, thank you. I will write up any positive information as I progress.
zip439, point taken, I should have checked the obvious first so will run a check on the harness wires back from the under wheel arch connections just in case some varmint has had a chew. I had previously checked out a full set of speed sensors which I had changed when I first got the car, the readings varied between 0.8 and 1 kiloohms which did not give me any confidence to identify which sensor was the culprit. This reading also seems a little low as on other cars I know of it should be between 1.5 and 1.7. A reading that continues to climb indicates a duff sensor. I will pull the 50 amp fuse and let you know the outcome. Love some of the mods you have made to your XF, do you know of any SRT6 look alike spoiler supplier, although I do not need a spoiler I think it might just improve the side on looks of the rather canine looking back end. Getting rid of the original spoiler would be a bonus anyway.