Copy and paste seems to change size

[ptoye]

I think you're right. I think that I must have created the new page from a template saying A4 size at 200 ppi and manually changed it to 300. I suspect that this means that GIMP creates a new page 2/3 the size of an A4 sheet but keeps the pixel count the same. Sorry to have troubled you.

Also sorry for the late reply - I needed the music I was editing for a gig yesterday and didn't have any time.