Got a great tip the other day from an electrician, and it works a treat. Once the holes for downlighters have been cut out in the plasterboard, get some pva on your finger mixed with a drop of plaster and smear it all around the exposed cut edge of the hole in the board. When it's set, you can then take the downlighters out any time without the plasterboard edge crumbling away...... Apologies to anyone who has known about this for years!!!
Roughcaster.