Wheel size for s3

I have 18" on a standard, (ET56), offset with Weitec Coilovers, 225 x 40 tyres. This still gives me some comfort when driving on the standard of roads that we have in the UK.
I know there are others on the forum running 19's on lower profile tyres with no problem, but, they are prone to damage because there is less rubber to protect the wheel.
It's all down to personal choice, really.

This chassis isn't made to take 19" wheels although many people do use them and I've seen some mk5 Golfs and A3s with 20" wheels...

I personally think that 19's are a perfect fit as far as looks go with a little lowering at 25mm front and probably 15/20mm at the rear. I mainly opted for 19's due to brake clearance but I was also tempted by Speedline Turini in 18's due to the low weight. In terms of ride I haven't been able to tell any difference at all. Mine is lowered a tiny bit from stock and with one heavy weight or two people in the back it does rub on the rears every so slightly but this is down to the lowering and the ET that my 19's are.