As for registering air rifles. You can thank Carlos the Jackal for that. He reportedly was a fan of using them in countries where obtaining firearms was nigh impossible.
There is a difference between a sub FAC 12ft/lbs Air Rifles and a FAC Daystate 0.303 Calibre Wolverine Air Rifle.
http://www.youtube.com/watch?v=Ysvz378TtjwThere really seems to be little understanding of lethality capabilities from the Politicians though.
This is even in the area of knife use in crime. Most assaults in Scotland is made using Kitchen Cutlery, where there are no sale or registration issues for folks aged 18+