If the car has been given a Cat S marker then it will have been previously damaged and repaired by an insurer. It is not illegal to repair and resell Cat S cars but the dealer must disclose any known damage to the vehicle when showing it to any potential customer.

I would advise taking the car back to the dealer that sold it to you and demanding an explanation. If you are happy to keep the vehicle then you can negotiate a partial refund to reflect the Cat S status of the vehicle and lower market value. Or you can demand a full refund, minus a fair deduction for the usage you've already had from the car.

If the dealer refuses to play ball then you'll need to seek legal advice. I would also report the dealer to Trading Standards.

For your consumer rights, see: www.honestjohn.co.uk/how-to-reject-a-car-your-cons.../