:D thanks for replies.Have now sorted it out- the limit stat had tripped when the boiler was heating up after refilling-possibly still air in heat store.reset that and burner fired ok.CH would still not work so I rechecked for voltage on pump terminals and found loose connection on live.Cable...
I have a powermax 135. CH stopped on Fri. Hw working Ok.Pump hot and also slight leak.Changed pump also isolating valve either side as they decided to leak when turned off so had to drain down and refill.Restarted and burner ran until water was hot.Then nothing.Burner will not fire at all even...