Free energy monitor
On a visit to my local library today, I discovered they are offering the free loan of an energy monitor for a two-week period as part of an initiative from the energy saving trust. This gives you a moment-by-moment update of how much electricity you're using, so you can track down wastage e.g. from things left on standby. They only had one at my local library and it was out; but it's part of a nationwide initiative so if you're looking to get a handle on your energy usage it might be worth finding out if your local library is offering the same thing.