Roger Mills wrote:

There is a fixed panel alongside the vanity unit, which is 500 wide and
about 1860 high, then a folding door - which is open in the photo. Does the
fixed panel alter the zoning definitions?

It would if it was 600 wide and went up to the ceiling...

[...]

I *could* chase it in to a depth of 50mm, or I suppose I could join it to
SWA above the ceiling, and bring the SWA down and through the wall. I might
even be able to join the cables below the ceiling in a universal box, and
then poke the box up through the hole - but I doubt whether 6mm SWA is
flexible enough to allow that.

6 SWA isn't /that/ unflexible - buy your length and play around to get
the feel of it. Why not join the cables up in the loft in a metal
adaptable box fixed to the woodwork somewhere (not poked up thro' a hole
and left flapping around)? Then you can bring the SWA out through the
en-suite wall wherever you like, because it's a protected cable. Drill
through the wall at an angle, sloping downhill and round off the lower
outside edge of the hole, so the SWA can be dressed against the wall at
its exit point.

I presume a new direct SWA run from the consumer unit to the garage is
out of the question.

It's highly undesirable, involving interfering with the decorations in
several rooms, moving a lot of furniture and and taking up a lot of floor
coverings and floor-boards. To be avoided if at all possible!

That was a rhetorical question ;-)

--
Andy