boiler element overheats and trip manual reset

This has been a recurring problem in the last 2 years. Very often it sorts itself out but not this time.

Around once or twice a year in the last 2 years, my electramate 2000 (not sure if its 9or 12w / 3yrs old) would stop giving hot water / heating for around 12 hrs. Then it would sort itself out. No switch off or any tinkering required.

Last week had the radiator pump replaced (2 yr old pump / no ceasing / replaced by electrician appointed by insurance company). Had no problem for last 6 days and this morning no hot water / heating again. Electrician previously advised me that when that occurs it could be the manual reset jumped due to overheating, so I took the cover off, reset (power still on) and the boiler element would heat up straight away BUT it boils the water and eventualy trip the manual reset again.

Turn hot water taps on and no movement detected on any of the 3 pumps. None of them ceasing (opened cap and smooth movements when turned). Warm water at the heating return pipe so i assume the heating pump is OK (just replaced!). Heat exchanger is cold. I do not have a multimeter to check the pump.

Could any one offer me any advise as to what problem it could be? Hopefully the insurance company would come back to me tomorrow and arrange someone to have a look at it but they are NOT gledhill specialist (they sent a plumber and electrician separately to change the faulty pump). It sounds like an underlying problem as it reoccurs once or twice a year and this time round its not fixing itself. Any help or advise would be most appreciated.

sounds like store pump to me