Hollow wall repair help needed

[Bob5998]

Hi, have an issue with a wall that I thought was a stud but id actually hollow with egg crate type filling. I need to repair some holes left after tile removal. Was thinking of squaring off the hole and adding in fresh 12mm plasterboard using grip adhesive, no studs to crew into. Or could use a finish compound to cover?

Any ideas would be appreciated

 

[Wayners]

12.5mm plasterboard.
Blob some plaster or easyfill or toupret powder filler on and stick board on