How can I remotely control electrical devices?
There are a large number of ways to do this - lots of people DIY it, but there are very simple commercial solutions out there too.

X10 is probably the best known standard.

Have a look at the UK home automation site for lots of info.

A bit more fun if you are a gadget freak or a tinkerer is Electric Imp - started by a guy from google and the guy who designed most of the iPhone hardware (as well as designing the best car stereo ever - even now 15 years later) - this device lets you make any device in your house Internet controllable :-)