Yeah I thought they all had it, what model and year is your car?
I'm not sure if the tints help, it's the fact that the heat gets in and can't get out...
They probably wouldn't do any harm
Leon mk2 + no a/c = UNTRUE SURELY.
Try the new Crystalline series from 3M. CR 70 is almost clear but with great heat reduction.
I am going to install crystalline to all my windows tomorrow and I'll let you know.