First problem encountered and solved by
me.
The existing hot water radiator encroaches a few centimeters into the space where the shower cubicle will be sited. It is a bulky double rad too big for the room anyway.
They intended to move that radiator to the other side of the room adjacent to the toilet.
(extensive extra pipework and a naked walk across the room to reach a towel

)
I volunteered to fund the cost of a 40cm wall mounted heated towel rail which solves the problem.
Now why didn't they think of that?
Ordered, paid for (by me £40), will arrive tomorrow.
I must say that my new WC looks good without that unsightly pipe between bowl and tank.