Electric Boiler planner not coming on but immersion works intermittently

OpolE

FULL ELECTRIC / No gas

All the power went off completely in The whole flat.

No mains switches were tripped however I noticed the boiler heating for hot showers finally stop bothering by the next day. I flipped all main fuses off and on again. 

I have had a few weird times where there was no hot water so may be on its way out or the clock is just losing itself.

So what I've done:

All fuses changed on the actual button(s) area next to boiler. (Immersion / Water Pressure Switch / PlannerClock Switch)

Planner and clock not working at all. I can set a plan, change the time, reset the clock to midnight Sunday and doesn't start dead on midnight plan. No other time of the day works either

Immersion Heater goes on for a while. Drops off for 10 seconds. Then goes back on. I can get full hot tank out of it so that's not too bad to work with right now for hot showers.

It was hissing hard the first time I was using it recently but looking at the smart meter and listening the immersion heater its doing work in bits. Seems a bit weird.

BOILER DEMONSTRATES IT HEATS SO SHOULD I FIRST GET SOMEONE TO LOOK AT MAIN FUSE BOX? DANGEROUS TO REPLACE FUSES WITHOUT KNOWLEDGE?

What might be the issue? Maybe 2 issues...

OpolE

FYI looking at the SmartMeter. The OVEN seems to be intermittent at heating too. 

Ectophile

OpolE said:

FYI looking at the SmartMeter. The OVEN seems to be intermittent at heating too. 

That's normal.  The oven should take perhaps 10 minutes to warm up, then switch on and off as required to keep the temperature you set.

OpolE

Hmm- Last night. 2 hours of immersion intermittently going off but mostly on. 5 minutes of hot shower then become very very cold. All sounds buggar'd now