Update on this - I downloaded the wiring diagram from ford etis and worked through what equipment it had fitted.I traced the medium speed can lines to the trailer module located ns b post.It had twelve volts on the can lines so I suspected a fried module of some description.
The van had been valeted on the weekend before it had broken down and the result was both footwells were full of water underneath the plastic steps. It had an aftermarket tow bar and wiring fitted with a canbus relay under the step sat in the water. The ford factory fitted module is on the b post but it looks like it was easier to drill a hole in the step to thread the wiring into the cab and put it there in a place where water collects ! Once unplugged communication was restored and the dash back on.
Thanks Andy for replying - I take it you've seen this before !I had got to it before I checked back on here to see if anyone had replied.
Phil