How to fixed an Prima F50?

Hi

Boiler working fine, never a problem. Our Estate had a power cut that lasted a couple of hours. The power came back on at half power, then full power. I noticed the power to the boiler was out. Checked the 3 amp fuse on the wall scoket on/off switch, this had blown, replaced the fuse switched the power back on and pop the fuse went again.
Has some circuit stuck open.
Thanks