Thanks again for your reply.
The Crank signal voltage was corrected simply by removing the Cam sensor connection. In doing so it corrected the voltage and also allowed the engine to idle properly.
Out of interest, we disconnected the crank sensor and scoped the cam signal assuming that we would get a waveform at cranking speed. To our surprise, the engine started and idled perfectly, and also corrected the cam signal voltage in the same way,as the crank signal.
When both sensors are connected, the voltages return to -3 to + 1 etc and engine will not idle.
Is it important for the voltage to read between 0 and 5 v or is the ECU more interested in the cam /crank relationship?
Just to reiterate the original fault,
Car starts and revs to max revs with no performance issues.
Engine will not idle, cuts out almost instantly below 1200rpm
Improves when fully warmed up,but when switched off and left for an hour or so, fault returns.
No EML or stored codes.
We could be missing something painfully obvious ??
My head is beginning to hurt so lets see what tomorrow brings