These methods of reducing electricity usage cost up to £50, but should save you more than that within a year.
Frequently sold in DIY stores as 'security' lights, these are overpowered, contain sensors so they switch on automatically, and are usually very cheaply made. No one really needs a 500W lamp to illuminate their front garden or driveway, and there is no evidence that they reduce crime either.
These devices not only use large amounts of electricity, they are typically installed around 3 metres above ground level pointing horizontally. The result being that every passing car, taxi or moth will activate the powerful beam, which then shines directly across the road into the neighbours bedroom window.
If you want a floodlight, a far better option is an LED type. These typically use 10 to 50 watts, rather than 100 to 500. They should be mounted at roof level pointing downwards, so they illuminate the garden or drive, not the entire street.
LED floodlights do cost significantly more - £40 to £50 rather than the £5 special offer in the DIY shop. However over the lifetime of the fitting the electricity saved will be many times greater than the additional cost of the fitting. The lamps last for years (rather than weeks) avoiding the inconvenience of replacements.
If you just want to illuminate your front door or porch, a lantern type fitting with a 7 watt flourescent lamp will be entirely sufficient.
If your hot water cylinder has no timer, it is likely to be left on for extended periods.
If you use hot water at the same time each day, a 24 hour or 7 day timer will ensure that hot water is available when you want it, and avoid the heater being left on when not needed.
If you use hot water at different times, an alternative device can be fitted. This has a button which when pressed will activate the heater for 30 minutes, 1 hour or 2 hours. The heater is switched off automatically, and cannot be left on by mistake.
If your oven, fridge or freezer has a damaged door seal, it will use far more electricity than it should. The seal is there to keep heat in or out. With a damaged seal, the oven will take much longer to heat up. Fridge and freezer motors will run more often, and significant amounts of ice will build up inside.
Replacement door seals are available for most appliances and are easy to fit. Either contact the manufacturers of the appliance, or search one of the many spare parts websites.