Having decided that the best thing for the ceiling is to cover it up a false ceiling was constructed. As the original ceiling is over 2.5m high the 6" or so for some studs and PB is no prob. Also means the recessed lights and fan/light can be fitted in the PB, there is no way the old ceiling would have stood up to 6 extra holes being cut into it. Son's making sure the corner is square and level, 'cause that's the corner of the alcove that the shower tray must fit in. All plumb-bobs were in use.