It shows the ratings that are provided by food standards inspectors.

Ah, ok, but so does the official government website. I'd never heard of Scores on the Doors until yesterday.

The restaurants are proactively inspected but nobody is checking that the sticker on the door matches the real rating unless you do it yourself*. Some companies have been taking the piss.

* Which you can at the website you listed.

Make the sticker text + QR link to a website so anyone with a smartphone could verify them if they wanted.

This could work for products too: have webshops add links to verdicts of inspections and also put them on the boxes (in link and QR code form).