Don't make me cut'n'paste the UK law here again mate
UK law states that any applied product to the window of a car may only reduce the total incoming visible spectrum of light by up to 35% on the front side windows. Factory tint varies by manufacturer but is nearer 5%. As the police and other authorities have no way to actually measure this , just keep the certificate of installation that says you have used 35% film
TBH they are only really worried about the 18 yr old junk muppets that put 'black out' film all around
If you are over (say) 30 , have equal tint all round of a low (say 35%) grade then they will just leave you alone.
VOSA (Vehicle and Operators Services Agency) have spent £13,000 equipping a number of Police Forces with an American made "Pocket Detective" meter to determine the light transmission of tinted windows. West Yorkshire Police are known to use it and have successfully prosecuted drivers in the Calderdale area. However, a number of prosecutions have been made without a meter being used. North Yorkshire Police are issued with "Tintman" tint meters produced by Turnkey Instruments Ltd., which was developed in conjunction with South Yorkshire Police - so they will have them as well. So apparently do Cambridgeshire and Lancashire Police Forces.
There are moves to incorporate light transmission tests in future MoT tests. Windscreens are required under current Police guidelines, to have light transmission of 70% TOTAL and front side windows at least 65% TOTAL.
In the UK, tinting forward of the B post is not legal, following legislation changes in 2004
The legal limits of VLT (Visual Light Transmission) are a minimum of 75% for windscreens on vehicles after April 1985 and 70% for front side windows. (Clear glass is approximately 86%)
Non-compliant vehicles can be given a Prohibition Order which prevents them from being driven further and requires the vehicle to be recovered or towed away. You may be given the option to remove the film at the roadside. If you get prosecuted it will likely be a CU20 Offence code, 3 points and a £60 fine.
Tinted windows should be declared to insurance companies as they may regard the tint as a facotr in the case of a collision which could invalidate your insurance.
In the event of windows being deemed illegal, the tinting company themselves will also have committed an offence under Section 76 of the Road Traffic Act 1988.
If you want "the look" you may as well buy yourself an Astra van in black
(And no I'm not a fan lol)