Seeking confirmation as to correct or 'normal' connection method for
an electric towel rail (around 500W) on a bathroom wall (which is well
away from the bath).

What I envisage is:

1 Spur from ring mains (RCD protected circuit) socket nearby outside
bathroom.
to
2 Fused switch on wall outside bathroom wall with a neon indicator
to
3 Unswitched spur connection unit with neon indicator near towel rail
(final connection by flying lead)

Intermediate cabling (1 mm^2 or 1.5mm^2) to be buried in chasing under
plaster.

Am doubtful about the cable spec from the ring connection to the first
fused switch. Should it be in 2.5mm^2 cable?

Any comments most appreciated.

TIA