Eric and David, Thank you very much for your very helpful replies. Firstly, here is the link to that review. Can't see how they will sell many copies via BT after that!
BT Shop - Microsoft MapPoint 2006 (B21-00801)

It is not very specific on the cause of the problem, just how it manifests itself. If the whole thing with the post codes is case sensitive then I guess I could solve it by putting everything in lower case but then I infer from what you say that if the full address is there then all will be well even if Post Code is in upper case. Would each line of the address need to be in a different cell in Excel?

My data set is 900 companies, 120 universities and 32 advisers dispersed in all areas of the UK. Thanks for your offer to do a trial with a subset of the data David, I may well take you up on it when I get the data next week.

I can't seem to find a free download of 2006 EU but will persist!

Regards and thanks,
Richard