low-voltage outdoor lights, with transformer inside house plugged into std
13A mains socket.

Problem is the transformer is ugly and not very discrete when fixed to wall
next to socket.

Solution. Spur current socket ( which is on ring main ) to provide power to
an additional fused switch next to it,
chase the switched supply, in conduit, down the wall to a 30A or 40A 3
terminal junction box located under the floor boards,
locate the ugly transformer in the void under the floorboards ( possibly on
a batten between joists to avoid it sitting on the floor )
Connect the transformer mains connection to the junction box.
Transformer would be located approx. 1 metre from the external cavity wall.

Is this safe practice ?
Would I be breaking any wiring regulations by doing this ?

Other comments?

TIA,
Jon