Gents, lots of options to explore, the MAF seems a likely culprit. I just wonder why rolling the car forward a few inches, in gear, enabled a start to be achieved, hence my query on the camshaft or crankshaft sensor - the learned forum does not seem to agree with that, which is good as that would be a job to replace. Does anyone know the part number for the S1 MAF? - as if I strip out the old one to clean it, I might as well just replace it as the part itself is not terribly expensive. Thanks again for all of your advice so far
I think rocking it in gear is far more likely to be vibrating/moving a poor electrical connection than anything else.
The sensors you mention won't really change state with that little movement in 6th gear I wouldn't have thought.