Ok, the guns are expensive (for my budget)

Off the shelf weapons are available and the china clones are cheap enough for anyone http://www.actionhobbys.co.uk/ http://www.airsoftscotland.com/ are two that I use so have a look, but before you try and buy read the rules about buying a gun as you need to get UKARA registered first, you can also get the defense in other way's but look on the forums for more info.
Have fun