The 'Economy 7' and 'Economy 10' times vary between electricity suppliers, Maydup.
Quote 1:
"Economy 10 times differ depending on where you live and which energy supplier you’re with. For example, there could be:
Three off-peak hours in the afternoon (e.g. 1pm – 4pm)
Two in the evening (e.g. 8pm – 10pm)
Five overnight (e.g. midnight – 5am)
Scottish customers are more likely to get:
Three hours in the afternoon (e.g. 1pm – 4pm)
Four in the evening (e.g. 8pm – midnight)
Three in the early morning.(e.g. 4am – 7am)
Some areas and Economy 10 electricity suppliers change these times when the clocks go back or forward – so your afternoon hours could be 2pm to 5pm during British Summer Time and 1pm to 4pm in the winter during Greenwich Mean Time. Other suppliers may not change the hours. Either way it could mean that for six months of the year the off-peak hours are less suitable for you"
Source:
http://www.ovoenergy.com/guides/economy-10/
Quote 2:
"Economy 7 times differ depending on where you live and which energy supplier you’re with. For example, the seven off-peak hours might be 11pm to 6am, 12 midnight to 7am, 1am to 8am or even 1.30am until 8.30am. You would need to check with your supplier.
The hours usually change when the clocks go back or forward – so your Economy 7 times could be 1.30am to 8.30am during British Summer Time and 12.30am to 7.30am in the winter during Greenwich Mean Time.
Occasionally a company will divide the seven hours into two or more periods, so that your electricity cost would alternate between the two rates during the night. Once again, it’s important to check with your supplier exactly when their off-peak hours are, to make sure you don’t use appliances during peak times by mistake"
Source:
http://www.ovoenergy.com/guides/economy-7/
As others have indicated, Fabemmy, storage heaters are designed to run from a separate electricity meter, so that you only have them taking power at the cheap times of day or night. Rather than giving out all their heat straight away, they store it up and gradually release it throughout the day. In practice, they're extremely useful for people who are at home most of the day (such as many pensioners) but possibly less so for people who are out at work all day (as they're not at home when their heaters, that have stored up heat overnight, are then ready to heat their rooms).