Question Author
The main fuse i refer to is NOT the electricy board one mentioned by Tony V,
Some older systems people have fuses which, if they blow, you simply push a button in to reset it. Even older places have wired fuses. My 2 year old mains fuseboard has a number of flip switches on it with different ampere ratings for circuits like lighting - upstairs sockets - cooker - downstairs sockets. If you need to isolate a single circuit you simply flip it to the off position. There is also a main master switch which simply turns off ALL the individual circuits in one go.
So on the first occasion it was simply the lighting circuit flipswitch which tripped (no lights in all the house) but the second time it was this main master switch which flipped out hence no power at all, Reset and all was well EXCEPT the WC light