geoff wrote:
A microcontroller just to give you a 2 minute delay - bit of an overkill
isn't it?

Yes, unless microcontrollers are already being designed into the system.

My house has 4 zones + DHW, yet there is just one thermostat. The zones
must be controlled by flicking switches behind a kitchen unit...! I
think whoever installed it was good at plumbing but knew nothing about
usability.

I'm currently working on controlling these in a more convenient manner,
using one or more PICs.

Ewan