From the legislation you quoted:
an air weapon (that is to say, an air rifle, air gun or air pistol
Yes - most wont consider a bling tourney gun as a weapon, nor a black 'woodsball' one as a weapon depending on look
But legally they are still 'air weapons' - note the guidnace document linked below, page 2, second column, 'air weapons and the law', 2nd sentence
I didn't say the boot of a car is a public place, I noted two scenarios - transporting and carrying in a public place. Not everyone is in a car, and 'transporting' is just that
Cylinders are not stuck to paintball guns, the cylinders are designed to be unscrewed
I still state that a cylinder fitted to a transported paintball gun is legally a 'loaded air weapon'
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/117804/air-weapons-safety-leaflet.pdf
The chances of getting stopped, getting searched and the policeman not liking what you have are slim - and are more in regard to what you are doing and your attitude at the time
It's not likely that someone is going to get in that situation,
