Not specifically "airsoft", but in the case of DPP v Street a 0.5J Webley pistol was held to be an air weapon. The Judge (one of the most senior and respected Judges of the High Court, BTW) took the view that as the Firearms Act didn't define "air weapon" with reference to anything other than the specially dangerous provisions, an item that looked like a gun, had a barrel, and spat out pellets due to the action of air compressed by a spring, was indeed an air weapon. Although this wasn't the central issue in the case, it would be considered a binding ruling unless overturned by either the Co