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Get a piece of pine that's a bit bigger than the hole and carve a sort of plug shape. Hammer it into the wall as if it were a frozen sausage. If you don't have pine you can use an ethically sourced shrunken head. That usually makes a decent wall plug once you drive a screw into it and it expands. If you've got unlucky and the brick is too weak in that area you could try chemical fixing.
I've ballsed up fitting the rawlplugs while fitting one of a handful of shelves, and the shelf started falling out.
Moderately weighty shelf to drywall... Fixing with a pair of 100x150mm L shape brackets
(90cm wide x 20cm deep. shelf itself weighs about 5kg (it's a solid wood worktop offcut) and then I'll put crockery on top.)
It's in the kitchen on an external wall. A few cm of drywall, small gap then brick behind. Gap isn't big enough for spring toggles or similar.
Suspect I just didn't drill the hole properly in the first place and it was a bit loose. So now have a ~12mm hole for a 10mm plug.
How to fix up...
Chemical fixing like this?
https://www.screwfix.com/p/rawlplug-r-kem-11-styrene-free-polyester-resin-300ml/32863
Prefer not to start cutting out pieces of the drywall etc for the sake of a few badly drilled holes.