Filling medium hole in an internal breezeblock wall

[Grofit]

I recently had some building work done, but some odd bits were not done as we didn't know they would exist when we were carrying out the work.

Now the problem is when we removed a fireplace/boiler there was a hole about 10x15 inches which housed a little wooden doorway to access the boilers pump. So I am not sure as to how to best fill it.

I thought maybe I could get a breezeblock and try to cut it somehow to the right size to fit in, but it is a bit smaller than a typical breezeblock so it would require a lot of resizing, but it seems a bit too big to just fill with some concrete stuff.

I read a few other posts on this subject here and 1 person did the breezeblock method, and someone else seems to have used a mesh and filled it. So assuming I remove the wooden area and try to get rid of any excess nobbly bits and smooth the sides which would be the better solution?

Also because I know next to nothing about building, if I were to fill it, what would I use? The other posts seem to indicate a 4:1 ratio of sand to cement but does it have to be specific cement?

thanks for any info!

 

[noseall]

If you have a hammer and bolster chisel it is fairly simple to cut any masonry.
4:1 mix will be perfect.

remove any material back to brick/block, brush the dust out, damp down and re-lay the cut block and point.