Tchibo 'Watt meter'`

I'm thinking of getting one of these to work out exactly how much power my PC is using and to track a few other things. Obviously it doenst make financial sense as i'm unlikely to save £12's worth of power (once postage comes into the equation.

- is there another way of doing this. Something like a pc has a very variable power consumption so averaging it over a week or more seems the only sensible way to go.

- the one shown has continental plug/socket. Tchibo cant sell that in the UK can they?