Many thanks Roady, but 1 more question if I may

I got there in the end; I downloaded the tool to reduce the file size of the
oputlook folder below 2gb.  It chops off some of the file then you have to
use the scan.pst inbox repair tool to repair the file.

After several attempts, this worked and I was able to get into the file and
delete thousands of old messages and dozens of files with attachments ranging
from 20mb to all files with attachments over 1/2 mb. .  

I had expected this to at least halve the file size, but in fact it was
still 1.9gb when I copied it back to the original computer.

Ok so this now works ok, but I may go over the limit again despite having
cleared out all the stuff that made it go over the limit in the first place.

Is there something else I need to do (eg some form of defrag of the file) to
get it back to something that reflects the number and size of files within??