Thanks for that guys. I realised the questions were a bit `specialised` to say the least!

I hadn`t intended using A/C so no problem binning the mounting. I intend to use that area to mount the alternator anyway! The brace would be a bit more rigid bolted up to a casting (of some sort) than dangling on the end of a tubed stud.
I`ve still got the donor car but was fighting against having the immobiliser or indeed any more black boxes than absolutely neccesary! ( Particularly if I also have to have the Alfa key/change the steering lock). I have had an ECU from a Peugeot de-coded in the past by the ECU doctor so may try that.
The engine definitely had EGR, I had assumed all the 24vs did. However, if it`s not common, it would explain why the pin chart didn`t identify it. It`s now destined to end up in the same box as the evap canister and , hopefully, the immobiliser!

Again, thanks for your help.
Simon.