Advice for hole filling kitchen

[b_kennedy]

Hello. I have taken on the task of fitting a new kitchen. So far so good however I have a question. I had some holes and sections where the concrete on the wall had fallen away due to removing tiles. I had a bag of hardwall in the garage so I mixed it up and filled the holes in. I put a small skim of plaster over a section of it just to try my hand at it. The other parts I have filled I have left with just hardwall. My question is... is it okay just to leave the hardwall as it's going to behind cupboards etc anyway or do I need to plaster the lot?

I've also had channels cut in the wall for new wiring for plug sockets that are wired through trunking. Can I hardwall these too or do I need another filler?

Thanks

Ben