Cheap plugs are a false economy.
Go to Screwfix or Toolstation, buy some Fischer ones, some decent screws and a good quality masonry drill. If you go to Homebase or BandQ you will probably pay 3 times as much, absolute rip off.
I would be careful about drilling out the old holes, you may end up with large holes in the wrong place, it may be better to relocate the fixings slightly and start fresh.
Whilst I agree about cheap plugs being crap – in my experience I’d say the quality of the hole is as important.
Too small and you’ll muller the plug when you tap it in, too big and it won’t grip properly.
make sure you pair up the right sized drill, and right sized screw for your chosen plug.
(ex-kitchen fitter here)