Sparks wrote:

Firstly, in the bathroom, is it better to lay the floor tiles before fitting
the toilet and hand basin, then sit them on top of the tiles?
(I have a solid floor)

Yes - tile first: much neater.

Secondly, still in the bathroom, I want to install a shower cubicle in my
bathroom with a solid floor.
I don't really want to raise the tray, so can I just chisel out the floor to
accommodate the waste pipe?

Why don't you want to raise the tray? Much easier having it standing on
a plinth, all the more so with a solid floor. Apart from anything else,
if you do stand the tray on the ground, you'll need to be able to get
your hands under the front to access the trap/pipes etc to install them
in the first place. A plinth also gives access for servicing in the
event of any problems later. Plus, depending on the structure of your
floor, you might easily end up digging down through the DPC while
excavating your floor.

David