I just bought a cheap one off eBay, like this one, easy to install.
You could glue on insulated plasterboard, no batten required , but would not add value as such.A new low level loo would make it look more...
Run cable as Notch suggested then remote control switch for lights, all hidden.
Or plug in lights using a wifi switch , again all hidden.
Built in microwave often comes with a surround designed for 60cm wide unit and top and bottom are sorted with suitable sized infill panels.
Plasterboard, cement board? Is it a temporary cover or permanent?
Shed had caused penetrating damp , if wall was soaked could take over 12months to dry depending on weather .
No screws in the keeps doing may well have moved .
As John said no need to touch it, the salts will wash away in the rain .
They never tighten in thermalite in just get crushed by the bolt.
Rawlbolts pull straight out of thermalite and are much too large for kitchen brackets.
You would need a rail to spread the load points, pilot hole serves no purpose in thermalite.Concrete wall will take normal fixings.Special...
Thermalite blocks don’t hold plugs , use 150mm screws straight in, as many as you can .
Move the loft hatch.
Your hose has connector for garden tap not the push fit....
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