Our old hot water cylinder (inherited with the house) came with an
immersion heater wired via a 13amp plug. This hasn't been used by us for
years (since the thermostat blew, boiling the water and shooting it into
the loft!). It's been unplugged ever since.

I'm planning on replacing the hot water cylinder, and therefore need to
decide whether to fit an immersion heater or not. I'm thinking to fit
one, but not actually wire it in yet (or ever!). I have no intention of
ever wiring it into a plug! I know that's totally wrong...

Anyway, if I remember correctly (I haven't looked at it for a couple of
years), the socket which the immersion heater used to plug into was on
the one of the lighting circuits, which is wired into a 16A MCB (plug in
type for old fuse box). The other light circuit has, I think, a 6A MCB.

Is it permitted (I doubt it's recommended) to replace the existing
socket with a suitable double isolator immersion switch and wire the
immersion in that way? It's the only source of power in that cupboard,
and would be the easiest way of getting power to the immersion heater.

I just want to think about things for the future, rather than actually
going ahead and doing anything about wiring it in now.

Thanks

David