Personally I think the window tints look great! Love your A4 Avant looks very nice indeedy!
BUT all you need is one over zealous Traffic cop (& they ALL carry light meters} & you could be in the mire
http://www.nidirect.gov.uk/tinted-vehicle-windows-the-rules
How do illegal tints effect your MOT tests when they are due? Is it giving your insurance company a 'get out' in the (hopefully) unlikely event of a claim?
One insurance company I know has just booted a claim out as the Insurer didn't notify the insurance company that was some small sign writing on the car! Crazy!
Not being a stick in the mud or anything, I am just looking out for you my friend