Best for patching a small area (onto wood)

I’m fitting a radiator tomorrow ready for the plumber to pipe up on Monday. I’ve had to cut out four sections of the existing plasterboard (for the brackets) and add some wood nogins (as the distance between board and block is 60mm).

What’s the best way for me to patch this? Powder fillers seem too soft, is there anything harder setting I can use that won’t crack?

 

you patch it with the cut-outs of p/board thatyou cut out for the noggins, an finish with any skim available.
thers lots of advice if you search on this site for patching p/board - probly on utube as well.