After receiving the notice and charge from Hertz last year for disclosing my details, I received the charge notice last week for about Euro160 if I pay fairly quickly. It appears I was about 30kmh over.

What if I don't ?

Obviously I wouldn't use Hertz again and if stopped by the Rozzers I'd probably be in trouble, but I do have 2 fines from Australia which are nearly 3 years old and duly ignored.