I tried setting the php max upload size to 2mb, which woks fine - but the knock-on consequence is that large images that are uploaded on the attached page now can't be uploaded. Previously, they were upload and then resized, which wold bring the file size right down..
So, I've added a server validation and 'show if' text. 2 issues:
1) The validation doesn't work - NO files can be uploaded, irrespective of size.
2) The 'show if' text is permanently displayed, even if I go to different PgID number page.