Removing upstairs wall - running into problems!!!

I found a 3mm gap between floor and bedding mortar at back of cupboard. Front of cupboard is properly resting on floorboards though. Gaps filled with variety of steel strips as far as practicable.

New stud wall up and stiffened with ply. I've tried to make it as rigid as possible, and it's tied to the wall either side with plenty of frame fixings.

Next week should be better as I won't mind venturing outside to get things!

It should be plasterboard not ply, and I take it you're putting in sound deadening material before the other side goes on.

Plasterboard to go on top. Roll of rockwool in the loft to stuff the gaps.