Pulsacoil trips main switch

Hi, we recently moved in to a flat and during the day the Pulsacoil is fine with the boost button working 100%. At about 11pm - 12am (not sure exactly when), the switch on the mains for the boiler trips, leaving us with little or no hot water early in the mornings (unless we use the water really sparingly in the evening to have a little left for the morning). We leave the house by 7am, by which time the mains won't turn back on and keeps tripping. Over weekends, at round about 9am, I can manage to switch it back on and it stays on. One suggestion from the Engineers was that it is a relay or something, but his part costs £350 excl VAT - and this is after they already charged £90 for a 10min call-out. Do you have any suggestions or are you able to provide assistance before I spend this much money and it may not even solve the problem?

Thanks
Neilz

Could be a relay or the bottom heater, if only doing it on off peak.
Those charges seem a bit obscene to say the least.
Look on here for an engineer. Home page list of advertisers.
Or Google up for Gledhill repairs in your area as in town, city or county.
If not call Gledhill whom may cover your area. Again Google.
Or they may recommend some one.
I will say again, it is better when posting to state your location.
Perhaps more offers of help may appear.
Mike
MGC/H2O
Norfolk.