The message
from Mike W W contains these words:

Here is a sketch of my system:
http://tinyurl.com/rg6dp
(excuse the scrappy sketch)

Where do the feed and return ultimately lead to? If to the domestic hot
water how is that controlled?

I am planning to insert the programmed zone valve in place of the
stopckock shown for Zone 1 (or perhaps next to it).

Replace would probably be easier. I am not sure what continuing purpose
the stop cock could have once you have a motorised valve to control the
flow. To completely isolate the zone so it could be drained down
independently would require a stop cock on both legs.

If these zone valves don't cost too much, I guess the ideal setup
would be to have one controlling Zone 1 and another for Zone 2. Then
each can be programmed independently to suit the living habits of (a)
me, in the main part of the house, and (b) my tenant, in the rented
part of the house. Comments/advice much appreciated.

Sorry, no idea of the current price of zone valves but I think they are
well worth the investment. I wouldn't have gone that route otherwise.

--
Roger Chapman