Does it have to be a 2.4 computer?

I'm thinking same now, have contacted breaker on eBay...

Hi Scub I have just typed croma body computer in to google and there are five part numbers that i can pick out 51855156 1.9 auto 46846744 1.9 manual and three 51789318 468122230 51804075 which do not say. So make sure that the breakers computer is a match. The computer box looks the same as any fiat like my son’s punto or my other son’s idea could it be that the only difference is how they are programed for different functions on different cars?

Scub found this on the alfa forum this morris gent might be able to sort you out.

I recently had a problem with my 52 reg 147 where the sidelights would not work. After a lot of eliminating I tracked it down to the body computer. Alfa said it was not possible to use one off another car as thay had to be programmed in the factory to a particular car. I was quoted £320 for a new computer and about £100 to fit and do final programming!!
IT IS POSSIBLE TO USE AN OLD COMPUTER OFF ANOTHER SIMILAR CAR! If you know a good specialist. I found one in Buckley near Mold in North Wales. His no. is 07785 560560 and he has reprogrammed a computer for me which I got for nothing as the breakers yard said it was no good for any other car! His name is Andy. My sidelights now work as does everything else on the car . He has read my old computer and transfered data for keycodes etc to the new one. It is a lot cheaper than Alfa and to be honest he has more clue in his little finger than all alfa dealers put together .
Hope this saves someone some money one day!! Cheers Hermit

Hmm, I had to remove the body ecu today to get part numbers, I noticed if you pull the very bottom plug I get all the symptoms I've been having, anyhoo, after removing from car, splitting into its 2 parts, refitting, I've been driving the car since around 1400 (now 1900) and no issues. Normally starts it's nonsense after around 20mins.
I hope it was an oxidised connection overheating maybe?
I'll report back in a couple of days...

It's definitely fixed, thank for the perseverance =0)