And I am very grateful Sunray
Regarding overload protection, the pump is fitted with a 3A fuse in the plug - does this not help?
There is also a rather large 10uF capacitor fitted, I assume to help the motor start?
I know the pump also has a thermal cut out...
To be honest, as an alternative plan, I am wondering whether to fit a motorised valve (something similar to a zone valve in central heating), wired in with the pump. This would be normally closed, and open when the pump is switched on. Both could then operate on a timer. Would that be an easier option?