While there are plasterboard fixings available, securing a wall-mounted television to studs is the preferred method. Connecting to a solid structure, such as a timber frame, should always be considered before a sheeting material. Know the weights you need to manage carefully before using a plasterboard option.
But if you do have trouble locating the studs or they don't line up with the mounting holes, plasterboard fixings are available. You can fix the bracket directly to the plasterboard with four Ramset Super Wallmate Toggle Anchors. Each of these anchors fixed directly into the plasterboard will hold 20kg.
If you can, locate the studs. Mounts are often supplied with wood screws, if your home has metal studs you should use metal thread screws instead. 10G screws I would think are the right size and around 50mm long. - Brad
I've mounted many TV's for customers and have never had any complaints that I took the extra time to mount them properly. In fact it has brought me more repeat business because I didn't cut corners. There is no substitute for strength other than studs when mounting to plasterboard walls. - DCS