If something goes wrong with the electrics in a property most people, if they have not got any electrical knowledge themselves, immediately call out an electrician and usually this is the right thing to do and the safest. There are some occasions however when a qualified electrician is not needed for instance if the trip switch has tripped out. The trip switches are generally next to the fuse board and so can easily be switched on again. If they continue to trip it is usually an appliance that has a fault on it so by turning everything off and turning them on one by one the offending appliance can be found, and a repair sought from an expert.
Changing a light fitting is another time when an electrician may not be needed although it is important if doing so that the electricity to the lights is disconnected by switching the lighting circuit off at the fuse board before commencing. If you do not feel confident dealing with any electrical issue in the property it is probably wiser to get an electrician in to do the job.
There are certain electrical tasks that have to be done by a qualified electrician who is part P registered which means that they are deemed to be a competent person in the eyes of the local council. These include changing a fuse board, running a new circuit for sockets and lights and electrical work carried out in a special location such as a kitchen or bathroom where water is present.