Checking where to run the wires whilst the studs are only covered on one
side.

DIYnot says

"Shaver sockets can be install a shaver socket either by connecting to a
ring main with a junction box (see Adding a spur to a ring circuit from a
junction box) or from an earthed lighting socket. The spur from the ring
main must be fitted with a 3amp fused connection unit before connecting to
the shaver socket (see Fitting a Fused Connection unit). The fused
connection unit should never be installed in the bathroom.

Connection from a lighting circuit can be made directly, but must be
earthed. "

Firstly, is this up to date?

If so, it seems I have two simple options for the upstairs bathroom

(1) Drop a cable down from the loft which comes off the upstairs lighting
circuit
(2) Spur off the upstairs ring main and put the fused connection unit in the
wall outside the bathroom.

Going off the lighting seems cheaper and simpler.
What are the downsides?

Cheers

Dave R

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

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