Hi, thanks for your question.
My name is Tony, I can assist you with this.
How do you know the license plate was included in the price?
So why does he now seek to deny you the plate?
Then if he told you it was included, then it should have been included in the sale. If he cannot sell it, or will not let you have it, then this must be recognised in the price. As you would claim breach of contract and be entitled to the cost of a similar number plate (in fact, if he owns it, and is able to transfer it to you, you might be able to compel him to give it to you by seeking an order for specific performance from the court).
If he was obliged to sell you the plate, i.e. it's what you agreed, then you would be able to say you don't want it anymore at all without the plate.
Then you would have to apply to the Court to force him to hand over the plate if you want the plate.
You could always have the car without the plate, then sue him for damages separately.
Yes, a contract for sale is a contract for sale. It doesn't matter that it's a private sale. So yes, he would be obliged to sell you the car, irrespective of the number plate issue.
Is there anything else you would like me to clarify for you before we finish?
Are you there?