Electramate 2000 - possible pump failure ???

Can anybody help please?

My Electramate 2000 has burnt out Relay 2 and started to burn it out again taking out the relay in the bottom right hand corner. After changing the relay everything seems to power up for a few months with hot heating and water then hey presto burnt out again but after my electrician changed the relay this time we now have the lower thermo cut out cutting out straight away. After keeping the thermo cut-out held in for a few seconds the heating element seems to start to boil and kettle. I've seen something on the forum saying this could possibly be the thermo sensor, pump or PCB and possibly the relay burning due to a sticking pump, is this right as this seems to be the cheapest part to change as I have a sapre one to hand?

Any advice would be appreciated and many thanks from a disgruntled cold walsall home owner.

sounds like store pump to me lower left hand corner behind heater bottle, the heater will kick in when theres a demand and if the pump is not circulating the water through the bottle it will heat until it reaches its limit and then overheat. confirm that you are sending power to the pump on the acb its marked up on the right hand side, just check that you are getting 240v there.
hope this helps
mark.