I finally found the problem - bad grounds which cause an overload in the ECM damaging it or burning it out.
My ECM is a Digifant II 037 906 022AT KEN Made in Germany. The first working replacement I installed was suffix AH which worked but with a slight misfire and no idle. The second is suffix CS which works better but poor idle. I had to speed up the idle by adjusting the butterfly valve.
The car is now drivable with no complaints from my wife but I will try to fit the correct ECM when my friendly wrecker gets one.
I found this link (too late for me) but it explains things very well.
http://forums.vwvortex.com/zerothread?id=3291139