Help repair hole in wall please?

[Casey2005]

How do I repair this hole in a wall?

I’ve done some research and watched a few videos, but can someone here tell me what to do?

It’s a very old house, and this pic used to be a old fireplace.

 

[Wayners]

Fireplace needs vent if blocked off normally to stop condensation.
I've bricked up with vent in.

Is chimney capped off or removed?

 

[Casey2005]

Removed

 

[Wayners]

I can't see exactly but i would be looking at blocks, board and fill.
Hand saw and cut thermalite blocks.
Ready mixed sand and cement.
Do the best you can but get the blocks in.
Plasterboard over with dot and dab.
Fill and make good.
Paint.

 

[foxhole]

Cut plasterboard square and patch with new .