IMM wrote:

IMM's suggestion accords with my own thinking - I believe I could
achieve this by simply shorting Switched Live and Pump Live on the
boiler (so the pump will run if the valves are open but will still
over-run too). Is there any reason not to do this - might it upset the
boiler controller?


I can't see any reason why it would. The boiler would switch the pump when
needed. If the pump is not running then it switches, if running, it doesn't
care. The temperature in the house will be a little more stable with the
pump running all the time when on CH.

Drat - it's not so easy. The controller sees this as a wiring fault and
puts the boiler into lock-out. Now I look, this condition is in the
Fault Finding Guide.