A lot of these lasers are purchased by yobs on holiday and imported back into the UK from places where they are freely available - Bulgaria, Turkey, Cyprus, Spain and a few others.
Unfortunately UKBA cannot touch them because lasers are not prohibited.
As soon as our MPs get their heads out of their expenses forms and pass the appropriate laws then you may see a drop in the availability of these things. - although I suspect that it may take a fatal crash before something is done....