Just spotted this device in the Belfast Maplin store. I tried it out and it works nicely with my Sony 32 inch LCD that uses 20w on standby (well initially at least). After a few minutes on standby it switched it off completely.
You can use it with extension cords as well, according to the Energenie website:
"You can use Energenie Standby Shutdown with multiple plug sockets, but note that all connected appliances will be turned off when Standby Shutdown automatically activates."http://energenie4u.co.uk/index.html