Any tinting film as of 1st January 2004 forward of the B-pillar is illegal.
Some legal stuff for you:
The Motor Vehicles (Construction and Use) Regulations 1986 outline various offences relating to the glass and vision of drivers as follows:
Regulation 30 - a driver is required to have a full view of the road and traffic ahead whilst controlling the vehicle and all glass or other transparent material fitted to the vehicle must be maintained in such a condition that it does not obscure the vision of the driver.
Regulation 31 - specifies that all glass fitted to motor vehicles must be safety glass and either laminated or toughened. Perspex or other plastic material which does not fracture in to dangerous pieces can be used, but only from the 'B' pillar rearwards (rear side windows, and rear window).
Regulation 32 - requires windows to be of safety glass, but 32(10) specifies minimum light transmission values which are:
<ul type="square">[*]for motor vehicles first used before 1 April 1985, all windows must allow 70% of light to be transmitted through.
[*]for motor vehicles first used after 1 April 1985, windscreens/windshields must allow 75% of light to be transmitted through, and all other windows 70%.
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On 1 January 2004, amendments to the regulations were introduced stating:
Paragraphs (10) and (11) have effect in relation to any tint, film, or other substance or material applied to a windscreen or window as they have in effect in relation to the windscreen or window itself.
Regulation 32(10) does not apply to the rear side windows and the rear window, since the driver does not look through them at the road ahead.
