Thanks to all that replied.
However, after trawling through the AIP and ANO (let's face it - these documents need to be brought into the twentieth century i.e. being able to search for keywords or strings), I found the answer in black and white after a quick search on the net in the first few lines.
http://toandfrom.org/lightaircraft/ukairspace.html
Airspace in a nutshell!
Nice and concise, in plain english and found in less time than it takes to turn the first page of the ANO.