I have a new house that I need to put up all sorts of fixing brackets,
pictures, curtain rails to the inner walls.

But all the walls seem to be hollow, ie plaster board I think

Whats the best method of fixing into it ???

I've got some 'metal self drive plugs with screws' As these are about
27mm total length, what happens if I screw these into the plaster
board and there is something solid behind the board, ie brick or wood
battons etc.