Hi there Ken
Many thanks for the quick reply, much appreciated.
I did investigate getting a salvage part through these Find a Part type website, but no hits from any of them. In the end I decided to search on the internet for a new part. I struck gold in Google using the Fiat OEM part number for the manifold (7301274) which was very kindly supplied by my local Fiat Dealer. I found about 4 or 5 different German websites that sold brand new manifolds and eventually selected one with what I thought had the best price, including shipping. I placed the order late on Saturday and have today (Monday) received a confirmation email saying that the part is on its way via UPS and should arrive on Thursday. All in, the new part cost me a reasonable £180.
Whilst on the site I also noticed that they sold a whole load of other parts for my 1993 2.5D Fiat Ducato based Hymer.
The company I selected can be found at the following web address:
Hopefully all being well the part will arrive and will be fitted early next week. I'll let you know how I get on.