My son paid a deposit for a car,the seller has now changed his mind, he also signed a hand written receipt, my son still wants the car

First I moved your question to the legal section. The section you posted was introduction, please go back and introduce yourself.

Who is the seller, a company or a individual.

Also exactly what did the receipt say, just a receipt for the money or did it say for a car.
Was there a contract that stated how much the car was to sell for, and what the terms of the sell was?

And as a side note, did anyone have the car inspected by a independent mechanic

Thank you

Individual

Hand written receipt with car reg on, amount of deposit and sellers signature

With the Car reg info on the receipt, legally this creates a binding contract. However, your son would have to take him to court to enforce that contract. If he was offered his deposit back I would not waste the time going to court.

Thanks thought so after hours of trawling internet,
He has offered deposit back plus 100, its just so anoying and was a brilliant buy, we would preffer the car...

I guess legally, you can sue them for what ever additional money you have to pay for a similar item, but that is about it, and then the argument of what is similar, most likely if they are offering the deposit back plus 100 dollars, the courts would not be interested in this

Well live in the uk and after speaking to trading standards it goes like this
It is legally binding

1 invitation to treat
2 consideration
3 contract

He is liabble for all costs to us incured,
The deposit , insurance paid for, car inspection etc

But you have to make the claim through the small claims court,

As this man is emigrating on Tuesday we have agreed £200 comp

But if you wanted you could pursue even in australia through small claims

My feelings are hope he and his wife get bitten by something nasty : )

well live in the uk

It really is important to give a general location for your account. However, in this case, contract law is basically the same in the US and UK. As you found out. A binding contract exists, but you have to go to court to enforce it.