writes:

You could implement your originally suggested zoning, so each floor is
on its own time control, the only difference is you have one
thermostat per room instead of one stat per floor zone. This means the
room stats must control the rads in that room via a valve of some
type. Electricaly controlled TRV heads are available for under £30,
such as the Danfoss RA 2912.

That's not electrically controlled; it's a remote bulb
connected by a capillary. I've not seen a Danfoss
thermoelectric head for anywhere near that cheap. The link
Richard Skeen posted in the "Timer TRVs" thread for
Heatmiser in-line wax valves was the cheapest I've seen, but
I don't know what TRVs the heads would fit, and I don't know
how easy it is to get the heads separately.

--
Jón Fairbairn
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2008-04-26)