Pulled from a website:
What Are the Penalties for Driving With Faulty Tyres?
In the case of any vehicle, with the exception of goods vehicles and vehicles adapted to carry more than eight passengers, for every offence there is a fine at level 4 of the standard scale with discretionary disqualification with 3 Penalty Points.
Level 4 currently stands at £2,500 and each faulty tyre is considered as a separate offence, which can really add up. Two faulty tyres equals £5,000 and 6 points on your license, and so on. 
Offer the magistrate some dirty prison sex and he might go easy on you