Hi All and thanks for the replies,
Went back round the houses yesterday while I had it in the workshop in a non-start condition only to find I had no cam sensor signal.
Frustrating thing is it was one of the first things I tested and I had it in my head that it was good.
The trouble with this one was it was sitting on the edge of working all the time, so you have to keep checking to see whether the engine was startable, seems I must have slipped up and tested it in the startable condition.
I still can't understand why it should be speed sensitive as a Hall sensor should work statically, perhaps it was supply Voltage sensitive.
Always difficult when the customer is whinging about cost all the time, when the crank sensor did not fix it I should have put a cam sensor on regardless, but at £108+vat it gets hard to explain to the customer that you have spent another hundred quid and it still doesn't go. Spent much more than that in wasted time that I can't charge.
Thanks again Shaun.