Why windscreen prices differ every time (and why we ask for the VIN)

When you ring and say "I have an Octavia, how much is the glass", the honest answer is: I do not know. Not because we are dodging the question, but because one generation of Octavia takes eight different windscreens and the gap between the cheapest and the dearest runs to several hundred euros.

What pushes the price up: the cut-out and bracket for the assistance system camera, the rain and light sensor, heating, whether across the whole pane or only in the wiper area, an acoustic layer that damps noise, a head-up display, which needs glass with a special inner film, and the shade band along the top.

The VIN is the only reliable way to find out which combination sits in your car. It is in the registration document and on the plate under the windscreen. From it we can pull the exact part number of the glass the car left the factory with, instead of guessing from what you remember the dealer saying.

The second thing that moves the price is where the glass comes from. The original with a carmaker logo, the very same glass from the very same maker without the logo, and a quality alternative from another maker can sit forty per cent apart at identical technical specifications. We always put both options in front of you and say where the difference is real and where it is only in the printed logo.

Where we recommend the original without argument: cars with a head-up display and cars with a heated windscreen. There the alternatives genuinely differ, and you will see it on the first drive into low sun.