I know John, it's just the rebel in me. I've been haveing my windows tinted since 2004 with the same configuration (5% rear screen, 35% rear sides & 60% front sides) and I've never been stopped. I put this down to the fact that a, all my cars are not in the boy racer category i.e Corolla, Megan, Espace etc, b, the fronts are always lighter than the backs so they look more legal & c, I've been lucky.
I know it might happen one day so I'm not kidding myself but I'll take the wrap if it does.