TDS Plastic Collated Nails 19mm | Trade Discount Shop ME 606 | Trade Discount Shop
Try this Red Floor Pad 15″ | Trade Discount Shop
https://www.tradediscountshop.co.uk/?s=tds+buffer
https://www.tradediscountshop.co.uk/shop/tds-saw-blade-to-fit-piranha/
must be your end?
Ditra matting
And bedroom looks like it has a door but no wall, primary bed misses the alcove where doors are, and all miss the doorways apart from bedroom that...
Firstly grind that lot all off, take a moisture ready see what RH it is , then go from there.
If you can't afford doing right then just leave it as anything you do with it will wasted time and money.
If the Magnasite was installed in the 50's > 70's then I would say anything under that is the same age. So I doubt you even have a sheet membrane...
Did you not have a look first, or was it just over the phone?
Problem you are going to have is once you start lifting around that area you'll be going all the way with it.