No hot water, boost works, safety switch tripped, burning smell

I currently have a standard setup - a pulsacoil a class with an off-peak timer heating up overnight and of course the boost functionality to use when I need more hot water. Now, a couple of weeks ago, the boiler stopped heating up the water overnight, though there weren't any errors, no red lights, it just stopped. I used boost for a few days then went away on holiday.
Today, I found that a safety switch for the boiler had been tripped and was now off. I turned it on. Few hours later, at exactly the time when the off-peak timer kicks in I hear a loud bang (and I mean LOUD!), lights flicker on and off in the flat and the safety switch is off again. On top of that, there's a horrible stink of burning plastic coming from the boiler room, though there's nothing visual as far as I can tell - haven't removed the cover yet.

So I guess there's two issues I would like to get an opinion on. First of all, what would cause the boiler to not heat the water overnight and how is that connected to the safety switch being tripped? If I'm gonna call someone to check on it, I'd like to be at least a little bit informed as to what might be the issue, so as not to get fucked over.

Thanks!

Well first of all it is down to you to find someone who knows what they are doing.
Check them out.
Ask neighbours whom they use?

Your problem could be;

The time control for off peak
The cables / flexes ( loose connections etc.
Relays (quite a few.
Off peak heater
The unit has water I presume ?
Mike
MGC/H2O