Control home's electricity sockets via PC
X10 works, but is a pretty bad protocol. It is very slow and limited, and is susceptible to noise and interference (often mistaking noise for actual commands, causing lights to turn on/off on their own). 

Z-Wave provides similar capabilites, but is much newer and uses RF signals to communicate. There are a huge variety of products and lots of stuff for UK (some stores I found on Google -- no endorsement: Z-wave products UK, UK Automation)

UPB is another technology, though it doesn't appear to be available in Europe.

Insteon is a fairly popular one in North America, and although they've been talking for a few years about introducing it to Europe, it doesn't appear they have yet. 

All of these (including X10) have ways to communicate with them from a PC, and from there you're limited only by your imagination and programming abilities. I have an Insteon setup in my basement home theater, which is controlled by a PC (and via the PC, can also be controlled from a simple iPod interface, my Aastra VoIP phones, or infrared remotes). Next house I will probably do UPB though (specifically, Simply Automated products), simply because the switches are a lot more powerful, and their software is miles ahead of Insteon, albeit also harder to use**. 


  ** Insteon is dumbed-down a bit to make it easier, but of course sacrifices some flexibility by doing so. My biggest gripe is you can't set up a scene that turns some things on, and others off (such as my "movie" scene does); the best workaround is to dim to 1%, which keeps my halogen pot lights still very dimly lit, and wasting power.