i wouldn't go that far mate lol
just some info from the UK Airgun law's
1) It is an offence to have an airgun in a public place "without good reason"
2) It is an offence to discharge a firearm within fifty feet of the centre of a highway.
TBH i don't think carrying it in the car for the reason of you might get car jacked will stand up well in court...
just so you are aware of the facts.
Carrying a loaded Air-weapon in a public place carries a sentence of 6 months imprisonment and / or £5,000 fine.
Probably best to carry a tire wrench like the rest of us