you cant just return it with out proving it has a fault annoyingly. getting them to accept it has a fault then i can get my money back and my PX if its still there. it does have an mot now this was what i saw with them trying to get it through one
But it does have a provable fault: It used over 4 litres of oil in under 1000mi, which isn't even close to being within the Nissan spec.
Doc's right, I would get it back to them with a final letter and request a refund or else go to court. And I would follow through with that threat as well: It's easy enough to do, and they're not going to challenge it I promise.
But i do need to let them look at it first correct?
As has been said just reject the car and return it as advised above: Simples: