Right let me try and help you in this context!
Using the latest Guidance on Firearms Licensing Law as of March 2015
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/417199/Guidance_on_Firearms_Licensing_Law_v13.pdf
According to Section 1.1, the definition of a Firearm is:
"A Firearm is defined as a lethal barrelled weapon of any description from which any shot, bullet or other missile can be discharged"
Reading straight on to section 1.2 states:
Low powered air weapons are not licensed in England and Wales unless they are of a type declared specially dangerous by the Firearms (Dangerous Air Weapons) Rules 1969 but there are restrictions on their sale.
Hmm that restrictions on their sale sounds a lot like "UKARA" to me?
Section 1.3 tells us what "Specially Dangerous" means:
An air weapon is “specially dangerous” if it is capable of discharging a missile with kinetic energy in excess, in the case of an air pistol, of 6 foot lbs or, in the case of other air weapons,12 foot lbs.
Pistol: 6 foot lbs = 8 joules = an FPS of 938FPS using .2g BBs
Rifle: 12 foot lbs = 16.3 joules = an FPS of 1326FPS using .2g BBs
However the correct part we are after in this guide in the regards to Firearms License is this Section 2.5 and 2.6 states:
Testing has been conducted by the Forensic Science Service on the actual lethality thresholds for airsoft BB 6 mm plastic pellets (0.2 grams). This work has become necessary in the light of the Violent Crime Reduction Act since a greater focus has been given to differentiating between realistic imitation firearms (often used for airsoft skirmishing) and firearms above the lethality threshold that would fall to be considered low powered airguns (or Section 5 (1) (a) prohibited weapons if capable of fully automatic fire).
Based on that work, we think it is safe to conclude that fully automatic airsoft guns operating at 1.3 joules or less and single shot (or semi automatic) airsoft guns operating at 2.5 joules or less would not engage the lethality threshold crossing over into stricter controls under the Firearms Act. This would mean that airsoft firearms that are also realistic imitation firearms operating at or below these thresholds would, nonetheless, not be required to be sold by a Registered Firearms Dealer but that the other control provisions provided by the Violent Crime Reduction Act would apply. Please note that this has not yet been tested by the courts.
Based on the above two paragraphs we can surmise that Airsoft weapons even those firing 6mm .2g BBs at even 2.5 joules of energy DO NOT meet the lethality threshold, because they DO NOT meet the lethality threshold they CANNOT be considered a firearm no matter how realistic they are, therefore it would be unlikely that he would be in breach of his Firearms Ban as that applies specifically to lethal barrelled weapons, furthermore I think a Firearms Ban specifically applies to him if he were to apply for a Firearms Certificate to own a firearm and that he is banned from ever owning such a certificate for any lethal barrel firearm. Airsoft weapons as realistic as they are do not fall under the same category.
However there are still restrictions on carrying these things in public, normal common sense (i hope applies).
In your case get advice from your local firearms officer or better yet the Firearms Licensing officer, the PC at the Police Station front desk will likely not know the answer to your question or even know where to find it.
I hope it helps by pointing you in the right direction.