Ah!..... the law, and "hope".
Alan reels off the law, making it sound easy and almost automatic, when it is nothing like that.
So you pay your £2000 court fee, (5% of claim, assuming boat was £40,000), find that the seller denies the claim, and you find that it is likely to take 9 months to a year for a hearing. Is the stress, anger, anxiety, worry, for all that time, worth it, as against getting it fixed, getting on with life and, where possible, doing what you can to help others to avoid such an experience at the sellers hands.
Having said that, we are still guessing as we don't know what are the faults, nor whether the boat was sold in the course of a business.