Thanks for the info guys.
I am fitting a new fuse box unit as a precaution, and also a 2nd hand body computer/ecu unit from another identical 147 1.6 TS. I am aware that the 2nd hand unit wont allow me to actually start the engine as it won't be coded correctly, but I am hoping that with it all connected up with the car, it will not burn out in seconds! If it remains in place without exploding I am hoping that way I may feel a little more confident before fitting the genuine (and very expensive!) actual replacement body computer.
I see on the link you posted that coilpack failure is often a cause of some ECU failures. My 147 was running perfectly, even when the ECU was smoking away for some length of time (and the instrumentation had failed too). Car drove normally for many minutes until I finally pulled over to park it. But clearly, as soon as I had to turn the car off there was no chance of ever starting it again - dead as can be (althought the engine does turn over without firing).
It was during the day, so I had no lights on, or stereo, or any electrical load outside of the engine/ECUs. However, during the period that the body computer was failing and burning out the electric windows refused to work at all. This meant the cabin now stinks!
I am going to remove the window ECU from the arm rest and see if it is visually damaged, or a likely culprit of the fault. The footwell is dry as a bone - I cannot see that anything got wet to cause the fault.