The National Grid site says
Your chosen electricity provider sells you energy but it's your local distribution network operator (DNO) who maintains the power lines that connect your home or business to our network.
In the event of a power cut contact your DNO to report it using the relevant number ....
Then there is a list showing the details for many areas of the UK, along with web addresses, phone numbers and more for each provider.
http://www.nationalgrid.com/uk/Electricity/PowerCut/
It's well worth spending a few minutes now to find out who you'd need to contact if your power goes down because of the storm.