update on the problem, spoke with the garage that did the timing belt for me and decided to take the car in for a scan, they also test drove the car.

Typically the car performed perfectly on the drive to the garage and test drive.

The scan showed no faults and live data looked ok.

So given the information found on the forum regarding the CPS i have booked the car in for the garage to replace it as the cost is very little more than I can buy the sensor for. They also did not charge me for the scan etc today.

fingers crossed that fixes the problem.