I got a standard manufacturers tint of 70% done on my F56 Cooper D last year by the company who is used by my local Land Rover, MINI and BMW garages.. Simply due to the fact my insurance provider wouldn't cover me otherwise. I'd go darker than manufacturers standard and say maybe 80-85% any more and you're getting towards limo style tints which I personally think just looks ridiculous. Please be aware though the film doesn't look anywhere near as dark in your hand than it does actually on your windows so make sure you're not being deceived!!