Thanks for your input that really helps. I do not have SPSS and that is probably beyond my level at this stage.
Your second approach will work, and is similar to what i was thinking in my badly written post above (sorry), i will lookup the _id values using the index each time and use that as the primary key in the database.
I somehow seemed to have overlooked the changing index field when i started with this but each time i have done a full import so it has not affected my data, going forward i would like to import only the latest data so will follow your suggestion to do this.
Thanks again, the support on this forum is great. Regards