Just thought I would update on the situation.
After several weeks of trying to avoid paying hundreds out for a new body computer, I have finally had a result. After speaking to several people (some helpful, some just looking to fleece) it was identified as a problem with the body computer. I spent a while trying to work out whether or not I would could just replace with a second hand re-coded body computer or if I had to buy brand new.
Anyway, after speaking to Neil at Alfa Spares in Lancashire, I took the body computer out and stuck it on a radiator - turned out there was a little condensation inside (common problem with 147's apparently). Once dried and replaced, works perfect!! The guy saved me £££'s.
I also spoke to Lewis @ Alfa Tecnico in Nottinghamshire... v helpful and I will definitely be taking my car there for servicing from now on.
So, if either of the mentioned read this... CHEERS!!