I use a motorized zone valve on the flow and a ball valve on the
return I can isolate a section of the CH circuit?

They do a reasonably good shut off but not enough to act as an
isolation if you want to do plumbing work.

Water companies are now fitting them as standard, or a charge as a
retrofit.
The quality has to be good, hence the stainless valves.

What, the water companies are fitting motorised CH valves as stopcocks?

Christian.