In article ,
T i m wrote:
My preferred method is to use a normal steel box. Fit wood battens either
side of the hole to the back of the plasterboard and fix the box to those.
That will never come away.

Good idea but that's assuming a plasterboard over stud or decent sized
battens. I'm not sure if this wall is all battens or dot-n-dab / mix
so the gap behind the plasterboard may not be sufficient (for the mini
battens). If it isn't then I'm probably going to have to chop out some
of the blockwork as well (but can then fix the box back to the wall).

Yes - if there is something solid behind the hole, fix to that.

--
*Not all men are annoying. Some are dead.

Dave Plowman London SW
To e-mail, change noise into sound.