I think the OP has a case.
He did not especially want to buy that particular specific car, his requirement was to be supplied with a particular model of car, and as long as it had a 2.0 engine, it didn't matter which particular car. They could have sourced one from any of their stock anywhere. In this case, the contract and the pre-contract negotiations were all about a type of car and a specification, and not about one specific motor.
He should argue that they agreed to sell him a type of car at a 2..0 spec at an agreed price and so they should do so. The claim that they made a mix-up with their pricing is not his problem, since the price was not manifestly absurd. For example, if you were buying a 100K Roller which was mistakenly advertised in an ad for £1 then that wouldn't wash legally, as any reasonable person is taken to obviously know that a major mistake has occurred and no court is going to enforce it.
OTOH if you are selling loads of cars, and you do misprice one, but not by so much that it is blatantly obvious it's a mistake, then a court may well say tough luck, the deal stands.
The OP went to a car dealership - not to a sweet old white haired lady selling her runabout. It seems the salesman locally didn't know that a 2.0L model couldn't reasonably be sold at the lower price, and clearly if an experience car dealer doesn't immediately see it is an obvious mistake, then it can't BE an obvious mistake.
I don't think it's a certain win, but well worth a go - especially since it would be a small claims case so no costs risk if you lose. And the dealership wouldn't want to be dragged through court. You could also threaten them with Trading Standards.