I started stripping back everything in my bathroom this weekend. The flat is a conversion. Long long ago it was an ironmongers, then it was a gymnasium (when all of the really poor decorating was done). The walls were covered in plastic (I guess for easy cleaning in the locker room?!) Anyway that is all gone now and I'm down to the original nicely plastered walls, accept there are a couple very large holes that I found. These consist of the chipped off plaster, some brick and also some cement or mortar.
They at least 6cm deep at the deepest.
What type of material do I need to use to fill them in properly? Mortar, plaster etc?
Thank you in advance for the assistance.