The front passenger and driver side window can only be tinted no less than 70%. Rear windows can be treated in any shade of tint. Windscreens must be clear from tinting apart from a 6" strip across the top.
If the police do a roadside check & advised to have the tinting removed, failure to do which might result in a prosecution and a fine of up to £2000
My brother had tints on hes first first car on the front side and passenger side as well as the back and he got pulled over by the police one night and given a knife to take them off there and then and as soon as he did it they wrote him a ticket and gave him 3 points on hes licience!