First of all, locate your consumer unit (fuseboard) and check whether the residual current device (RCD) and/or a circuit-breaker has ‘tripped’ (turned off).
An RCD is a switching device that trips a circuit under certain fault conditions, and disconnects the electricity supply. Circuit-breakers are automatic protection devices fitted in the consumer unit which switch off a circuit if there is a fault.
If the lights are not working, a lighting circuit-breaker may have tripped due to a bulb blowing. You will need to reset the circuit-breaker by switching it back on, the lights should now work. If they do not come back on, you will need to contact an electrician.
If it is your sockets that are not working, a circuit-breaker and/or the RCD may have tripped due to a faulty appliance being plugged in. You will not be able to reset either of the devices until the faulty item has been unplugged from the circuit. If you are not sure which appliance has caused the problem, unplug all appliances, reset the circuit breaker and/or RCD by switching it back on. Plug each appliance back in, one by one, until the faulty item (which trips the circuit) is found.
If you cannot reset the circuit breaker and/or RCD even with all the appliances disconnected, call a qualified electrician. Always use an electrician who is listed on the Registered Competent Persons website. This means that they are registered with a Government-approved scheme and can issue a certificate to prove that the work has been done properly and is safe.
Visit the Electrical Safety First website for more help and advice about what to do.