MS,
Working the problem the other way around as you suggested worked the easiest for me. I tried LauraL's suggestion, but ran into big trouble when I tried to run get script; with all the data still in the table. Once I deleted all the data get script; worked fine, and I'll be sure to keep that in my bag of tricks, but once I have all the data deleted it's just as easy to save that reduced table as a template then copy in the new data as required.
Thanks to everyone for all your help,
Mark