Convector/Panel heaters

Is

any help?

No. :o)

It wasn't the zone stuff I was worried about, since I already know about that. It was mounting a heater on wooden furniture and running cabling inside that furniture.

If I'd known the radiator in the bathroom was so useless, I'd have sorted it out when I refitted the bathroom. But I didn't. Oh, well.

why not, its permanent

could add a fan

NT

I don't see why not.

It's no different from an electric fan heater in a kitchen unit plinth. In fact that might work in your situation and not get obstructed by hanging towels.

Owain

Cabling etc under the bath is "outside" of the zones so long as the bath panel needs a tool to remove it.

The heater itself will state if its suitable for bathroom use, and also what limitations (if any) there are on mounting substrate. If you were particularly worried about the combustibility, then you could replace or clad the existing panel with PB or one of the cementious backer boards.

Towel rail type?

Yep. Already discovered that.

Nope. Standard pressed steel, but the flow through it is so miserable, it never gets very hot. I suspect it's been moved at least twice (not by me) and the plumbing is so byzantine that there simply isn't meaningful flow through it. Our en-suite (which is what we're talking about here) is a shed dormer and likely the coldest room in the house (although it now has 4" of Kingspan in the walls, as opposed to the few shreds of fibreglass it used to have) and needless to say has the most useless radiator. As I get older I'm finding I'm placing more and more importance on being warm ...

Nowhere to mount one of those, I'm afraid.

Have you tried the normal balancing routine to improve the flow through this one?

Pretty sure I've seen them with 15 minute timers though.

I have a Dimplex one which is nearly 30 years old. It predates me installing central heating and is also triggered by a remote frost stat.

Unfortunately, nothing you can buy today has anything like that longevity or servicability.