Hi Dave,
Thank you for your reply and advice. I just contacted BMW UK and the put me onto BMW Group Classic based in Munchen. Unfortunately they responded: "The BMW Group Archive is currently in the process of moving its inventory to a new location and is therefore only operating at a very limited capacity. For this reason, we are unable to process any inquiries at the present time and cannot issue certificates" I can't establish when and where my car was made therefore.
I don't suppose you happen to know if BMW produced non-CSI versions of the 633 in or around 1978, or were they all 633 CSIs? I have always though mine was just a 633 but I cannot find any reference to a 633 only model on the internet, only CSI models. If they did produce 633 (non CSIs), I wonder if they are more desirable than the CSI models?
Dean