Thanks for your enquiry.
I'm afraid that unless the monies being used to purchase the property belong to your Son (and you are purchasing the property as his Attorney, which you are not), you will be liable for the higher rate of Stamp Duty.
I'm afraid there is nothing you can do to argue your case with HM Revenue & Customs- it is your money, and you will be entitled to the proceeds of Sale as and when the flat is sold. Therefore you will be liable for the Stamp Duty of £4,850.
I am sorry this is not the answer you were looking for, but it sets out the legal position.
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