Cut a piece of 4" wide timber about 10" long, mark the centre of the length (5"). Partially insert a 35mm screw at the centre point, (this is to hold onto). Insert the piece of timber into the ceiling hole and centre it. Get 4 screws, and put 2 screws at either end of the piece of timber you inserted into the hole. Screw right up and through the original ceiling puling down on the screw you partially inserted into the centre of the piece of timber at the beginning. Once you have fixed the piece of timber into the ceiling hole, remove the temporary centre screw, cut a piece of plasterboad to size, then screw it to the piece of timber you've just fixed into the ceiling. Make sure you choose the right thickness of p/board,, (9mm or 12.5mm). Once you have all this done, tape over the joints, then flush it over with a couple of coats of Easifill or similar, then sand down an paint.
.
You could also repair it by cutting and screwing a piece of wire lath, (eml) over the hole. Screw the "eml" to any exposed areas of wooden lath. Once the wire lath is fixed, wet down and pva the edges of the plaster surrounding the hole, then using Bonding Coat,, plaster onto the wire lath, making sure you push the plaster well into the wet edges.. Do it in two coats then let it set. Once the patch is flush with the rest of the ceiling, finish it with multi. No need for taping doing it this way.
