Ok, the new dash is in with no major problems, time taken 5hrs and the extra time to refit to was down to a few things,
1) Spending time cleaning all the trim
2) Alfa forgot to drill one of the fixing holes in the new dash so i had a bolt with nowhere to go and finding where the missing hole was took longer than expected.
3) I ended up with a wire left over and despite pouring over the numerous photos i had taken i was unable to find anything to plug it into. I eventually concluded it is for some optional feature i don't have. Everything is working anyway.
4) The temp sensor in the top of the dash wouldn't go through the hole but i didn't discover this until i had bolted the dash in place so it had to come out again.
After reconnecting the battery and resetting the windows everything worked with no warning lights which was a relief. I will try and put the procedure together with the pictures in a separate post, it really is a fairly straightforward task with some basic tools.
One of the pictures below shows the state of the old dash with the vent removed and how much the leather has shrunk, it did look a bit naff through the windscreen so i'm really happy with the result despite the cost