As others have said, find the wooden battens that the plasterboard is attached and it is in these wooden battens that you want to drill your screws into, to secure the mounting bracket. Of course, if you have used decent, thick plasterboard, as someone mentioned above, it is possible to hang the brackets on the plasterboard and it should hold.
For the record, I dont think he is willy waving as 32" LCD tvs can be had for £350 these days.