I need to bring cables from upstairs to downstairs to the consumer unit.
Total around 10 T&E in various thicknesses.

The only relatively fool proof part of a wall is where the existing cables
come down and I don't want to remove these until the wiring is complete.

I therefore need to run them down a separate part of the wall - I have a 2
foot space between the kitchen door and the living room door that would be
ideal.. Sods law says that somebody will no doubt bang a nail in the wall
in the future, co I need to give the cables protection.

As I see it, I have the following options:

a) Feed the cables through metal conduits, then plaster over these. The
plaster will have to be a bit deeper than the existing half inch. The
cable from the shower would have to be placed out of conduit at the edge
of the wall.

b) Bury the cables in the plaster as normal, then cover with a sheet of
suitable metal for protection

and that's it! any other suggestions?

Would there be any problems with running a T&E cable (1.00mm and 2.5mm) in
a 10 foot vertical drop without any support?

Thanks

Roger