After lots of thought, I decided the best way to protect the carpet edges around the skirting was to use wide masking tape and tape it onto the carpet, pushing down the edges with a spatula into the space between the carpet and the skirting. I then added a second strip for wider coverage.
You could even tape the drop sheets onto this. It worked brilliantly, and made painting around the doors particularly easy!
By Sabre63 from Melbourne, Australia