Fatboise wrote:

A: Wire the power for the boiler through the motorised valves, if
they're all closed then the heating will switch of.

That would be good.

B: Build in a by pass on the plumbing, but I'm not sure how this will
work either. Do I need to add pressure switching valves or what???????


Automatic by-pass/Differential pressure relief valve, I think the
Honeywell one is called something like DU145. The pump differentail
pressure increases as the flow rate decreases, so the valve opens at a
pre-set pressure, allowing water from the flow into the return. It
maintains a flow rate through the boiler & pump until the boiler is
shut down by it's high-temperature thermostat.

The kitchen isn't a good place for the whole-house thermostat. You
could be cooking in the kitchen & the heat would shut off the heat to
the rest of the house.

What operates the other 3 thermostats? A thermostat in each zone is
usual; the boiler & pump start on a demand from any one zone.