WOO HOO .... FANTASTIC.
The revised PDF export, with the optimise for size, has made a HUGE difference to the size of the files for emailing, and very little difference to the export quality.
My last blueprint exported at 19,372 KB, which wasn't e-mailable - with the Optimise for size at 300 dpi (which is still more than adequate for emailed drawings) that was down to 6,455 KB which was perfectly managable.
Thank You.