Here to help . . .
Join Date: May 2010
Location: United Kingdom
Problem solved and car now running.
This is what I have learned and would therefore suggest to any others with issues:
1/ Always check ALL your connections first - these include engine earths, battery condition, all plugs to all ecu's/computers and all fuses. Check every relay you can and also check your immo aerial (ring around ignition barrel) BEFORE spending any money or looking any further.
2/ Until evidence suggest otherwise, you can not get these ecu's programmed easily (read that as 'cheaply' reprogrammed) SO the cheapest way is to find an almost exact model of your car (same engine, body style, features and age etc) and switch the engine ecu (found above the throttle body obviously), the body computer (fixed to the back of the main fuse box inside the car above the pedals) and also use the new key for the electronics (immo chop and central locking electronics). I suggest using the new key but putting your old key stem (the metal bit!) in it as the new ecu's will come with new coding for the central locking aswell as the immobiliser.
I hope this helps someone else in my situation.
I got the parts from a smashed 147 which was identical (except colour) and made sure it started alright first and removed the parts myself. I paid £100 for all the parts but most quoted £150. It takes no more than 20-30 minutes to do the entire switch.
I hope that helps someone. If you want more info, feel free to ask or pm me.