Yes there are fixing available from Screwfix, and the easiest ones are sleeved anchor bolts which expand in the wall and the sleeve extends to the plasterboard surface so the weight or load is transferred to the sleeve and bolt rather than the plasterboard. You may have to purchase a masonry bit of the appropriate size to suit the bolt. you will need to be precise when you mark the position of the holes and use a level and drill through with a pilot masonry hole then use the larger bit. There are other techniques for your fixing but his is probably the easiest if you have access to a hammer drill take your time don’t rush and it should do the job.
If the wall is “drylined” that is the plasterboard is stuck onto the blocks with blobs of adhesive, then the gap between the plasterboard itself and the breeze block is likely to be less than half an inch. Drill straight through the p.b and into the blocks then use the kind of long fixing plugs and screws used for fixing doorframes to walls. The same sort of fixings can be used if the wall is battened however care must then betaken not to tear a hole in the p.b. when you tighten the screws.
