Wee Rascal. From looking at the advert for the Discovery that was sold to you, it seems you have a very good chance of redress against the trader. When buying from a trader, no matter how big or small you have rights under the Sale & Supply of Goods Act 1979.
These are that the car must be of satisfactory quality (bearing in mind its age), must be as described, and must be fit for its purpose. This means that it
should be free from defects other than any you've been told about, should be exactly what you've been told it is, and should do what you might reasonably expect of it, including any particular purpose you have specified to the seller. The Discovery you bought is obviously not as advertised. The fact that the trader made you sign a disclaimer is totally irrelevant, as it is not legally binding, and completely worthless, also the term "spares & repaire is meaningless, the seller is merely trying to avoid his legal obligations. it is important that you do not drive the car anymore. Get the vehicle inspected by the AA, or RAC, and get a written report of any faults found. Hand a copy of this report to the trader you bought it from. The trader then has a choice of either refunding you and taking the vehicle back, or carrying out the repairs needed to bring it up to a reasonable standard. If he refuses to do either, then you should contact trading standards, again with a copy of the AA/RAC report, and give them the traders details. It may be that you have to end up taking this guy to the small claims court. If this is the case then I would strongly advise you to hire a solicitor that specialises in this area of the law. In the meantime, make sure that you keep a copy of any letter you send to the trader, make a note of the date & time of any phone calls you make to them, and who it was you spoke to, and if you go to see them in person, try to make sure you have someone with you who can act as a witness.
Good luck, and I hope it works out for you.