As has been mentioned here already, you need 2 things.
You need a bitcoin wallet to receive/store your bitcoin and to create transactions that send your bitcoin. For someone starting out, I'd suggest using
https://blockchain.info/wallet for your bitcoin wallet. You may also want to look into Electrum, MultiBit, Bitcoin-Qt, and Armory.
You also need to find a method of acquiring bitcoin. Like any other currency there are several ways to acquire bitcoin:
- You can sell stuff you own and accept payment in bitcoin.
- You can provide a service that someone else wants and accept payment in bitcoin
- You can exchange your local currency for bitcoin using a bitcoin currency exchange
- You can beg for bitcoin and hope that some kind soul will donate to you.
For the moment, lets assume you are going to try and exchange your local currency for bitcoin. You can look at
https://localbitcoins.com/ and see if you can find someone local who is willing to meet up with you and exchange their bitcoins for your local currency. You can wire money to
https://mtgox.com/ and use the electronic currency exchange there. I'm mostly familliar with options in the U.S. such as BitInstant and
BitFloor. A little bit of searching around the forums here and you should be able to figure out what options are available to people in the UK.
EDIT: As of 2013-04-17 BitFloor has ceased all operations.