looking at the estimated monthly payment is no good. Look at the kWh you use per year. Have you kept your electricity bills or meter readings? If not they should show the last 12 months usage on the latest bill, or if you are an online customer you can with some companies look up the meter reading history online. Look at your bill and your meter to check that you are paying the cheap rate for overnight heating on your storage heaters. Look at the meter during the night to see if all your electricity is going on the cheap register during the night, if it is, then use as much as possible of your electricity during those hours.
Electricity usage will mostly be for heating followed by water heating as I presume you have an immersion heater. The storage heaters I will guess use about five times as much energy as everything else in the flat put together. Look at your summer bills when the heating is off to see.
If you have a hot water cylinder, what colour is it, and how is it insulated? How are the hot pipes insulated? How hot is the tap water? Are there two immersion heaters, one in the top and one in the bottom? Are they both on timers? Do you leave the top one switched off?
Have you got a loft? How thick is the insulation?
Lighting uses very little but you can cut it by about 70% by changing to low energy light bulbs. Get cheap ones from the supermarket. A 100W filament bulb needs about a 22W CFL to give equivalent light, don't make the mistake of buying an low power CFL and then complaining that CFLs are dim. It is especially economical on lamps that are kept on for long periods, such as hall or porch lights.
A 20W low energy lamp runs for about 50 hours for 14p so don't fret about switching them off every ten minutes.
A 12W CFL is adequate for a bedside lamp, or for a landing light that you leave on all night to save falling when you go to the bathroom or to reassure a child. It will cost you about 2p for 12 hours so not worth worrying about..
A tumble drier will use in the region of 2kWh (30p) for a typical load.
An oven doesn't use much because it has a thermostat that turns the power off once it reaches temperature. Slow cookers use even less.
Despite what people will tell you, a phone charger uses an infinitesimal amount of electricity even if you leave it plugged in 24 hours a day. If you have 60 million of them in your home it will add up to a noticable amount, but you haven't. Modern TVs, decoders, DVD players, Hifi use very little on standby. A radio uses an infinitesimal amount.
An old fridge or freezer will use much more than a modern one. I chucked out an old fridge and saved £60 a year. All the chargers, TVs and lamps you can cram into a house won't use that much.
It's a pity you are on storage heaters, they are not much good unless you are at home all day while they are giving out most of their heat.