yes I've seen the plug in ones, but it's more the lights etc that I'm concerned with esp the kitchen where my wife insisted on 6 x 75W halogens
I keep telling her it uses tons more energy than the hallway light which is a single 7w energy saving bulb... she just sees the light (or not as the case may be
Your halogens seem rather high wattage ? 6x75 = 450 watts per hour is roughly 1 kilowatt every 2 hours . that could potentially be 3.5 to 4 kilowatts per day ! say £0.50 a day!
Switch to a 60w flourescent and it should reduce that to 1p -2p per day
lights are easy . you just need to know the wattage of the bulb and the length of time the light is on 100watt bulb for 10 hours = 1Kw your elec bill will tell you what you are paying for a kilowatt of electricity.
Lights are rarely responsible for any significant wastage .
Its the appliances like fridges and freezers that consume all the hidden electricity. They are high wattage items on constantly all day and night and as they get older they consume much much more than their design specification.
Tumble dryers are another biggy