Suggestions required for non starting polo 6N

[Tobz.]

Hopefully somebody can help out with some suggestions.
The car is a polo 6N with the 1.6 injected AEE engine.
Not starting due to no spark, I have established the following:

Output from hall sender fine (checked with an led while turning engine over).
Supply voltage present on the 3-pin connector to the coil (solid state) BUT no pulse present on the middle pin. I've checked the continuity between the hall sender output and the ECU and that is fine. I've checked the 12V supply to the ECU and that is fine.
The fuel pump primes when the ignition is turned on etc etc.

What could cause the low voltage signal to the coil to be interrupted?

Cheers
Toby