and the TP7000 is overkill for my requirements of adding a room stat
to a system which already has a timer.

Actually, it is very much worth having the timing functions in the
thermostat. This is because the programmable thermostat can do useful
things like dropping the temperature rather than just cutting the heating
totally, frost protection and set back.

Mine has a nighttime and daytime temperature and will estimate how long
it takes to warm the house up depending on the current temperature and
turn on at just the right time. This isn't possible with a separate
programmer, where you have to set it back manually by an hour or two and
probably overestimate the time required to warm up sometimes and
underestimate at others.

Also, it is extremely useful having the timing control nearby (I've got
them in the master bedroom and lounge) rather than in a dark manky
cupboard under the sink.

Christian.