i seriously wouldnt hang a thousand pound tv on a platerboard fixing

if its been baterned out its prob gonna be 19x38 or 25x38 batterns, theres no reason why you cant drill through into the block/brick behind and either plug and screw or as above a heavy duty raw bolt, im sure 4 8mm plugs either side with 100mm screws will hold it fine

if a rad drops due to shit fixings its only gonna fall 6inchs but if your tv goes its gonna smash and everything else below it

also youll be very surpirsed how strong platerboard is when its fixed at the standard 400mm centres so theres no need to worry about it giving way