Plastering internal brick wall

You should be fine using HARDWALL plaster, you can also add cement to it but it is your choice. Just clean the area of the wall first and apply 2 coats of pva.(diluted 1:5 & 1:3. If it is too thick, just put one layer of the hardwall (scratch it too if it is a big area) and once it is set (not necessarily dry) apply the second coat. Make sure it is just above the floorboards (you can lay a piece of timber, or scrape it off once it sets). You won't need to skim it as you are covering it with the brick slips. Hope this helps and good luck

My recommendation would be to fill the gap using a 'Filling Knife' (no need to buy any expensive brands or specialist plastering tools for such a little job) to parge some Bonding (type of plaster) into the 30mm hole, let this pull in (repeat if needed), you will want the bonding to be 2-3mm lower than flush with your wall. Once this has dried fill using filler and follow the instructions on the bag (alternatively you can buy a pot of ready mixed filler if the area isn't too big). Shopping List - Bonding Plaster (12.5kg and 25kg bags available read bag for an idea of how much you will need) Easi-Filler (again check bag to find out how much you need, or check the tub if buying ready mixed) Filling Knife

It doesn’t need to be a finished plaster , so you can just pva background and use bonding plaster

2 coats of sand and cement 1st coat slurry coat then second coat always yous sand &cement on the in outside of the outside walls