Duke link said:depending on where you live, you might want to worry, for me, i cant recall a time in the last 8 years the power went out for more than an hour.. london is probably similar.. if you lived in the country tho.. a plan would be needed.. as a last resort worst case for us guys with no plans you could use hot water in pop bottles from the sink to keep the heat up.. and you can oxygenate the water by dumping some water in the tank with a pitcher or a cup or something.. or go get a power inverter for your car.. and a long enough extension cord to run your return pump for a few minutes each hour if it goes out.
The hot water idea only works if you can make hot water without hydro and the vast majority of people will not be able to do so.....