Just to update this. I had the van again for a few hours and tried to make it fail but it started perfectly. Fitted the new ckp, gave it back yesterday, just had a call saying it failed again already this morning.
The customer had been informed that the part was being fitted based more on educated opinion than positive test results and if it failed again he would be faced with paying for more testing and being without the van for longer.

This brings me back to my inital thoughts that those codes could be red herrings because I have seen similar before. Getting it to fail and testing it is the only way forward as far as I am concerned. Hopefully my next update wil be a fix.