Meanwhile, in between preparing for the windows and doors (removing sills and old plaster, new base coat plaster & boards, new front door frame on the new, higher floor etc.) and struggling with floor frustrations, we have chosen, planned and ordered the kitchen and bathroom.

The kitchen will happen before the bathroom.  But the changed bathroom layout means re-configuring the soil pipe.  The soil pipe is cast iron, and runs inside the house, from roof to kitchen floor.  So that needs replacing with a new pipe and connections, before the kitchen is done.  And anyway, the old toilet leaked and smelt bad, so good bye.