Update on my issue. I had the crank sensor replaced, seemed to be ok this week driving to and from work, although the idle seemed a little rough. I was driving today and it stalled out again. Called out RAC to check things, asked him to check the installation of the crank sensor to see if it was an alignment issue. He checked the gap and made an adjustment. then driving home, once again in stop/start traffic it happened.
I feel like it is some kind of air issue, as it only seems to happen it hot weather, when the car is not moving fast so little air coming in. I have a diagnostic check booked on Monday, so hopefully I get a guru turning up who can figure it out