You have 3 attempts to pass then there has to be a delay before the next 3 attempts. How long that delay is I don't know, but I don't think you are grounded for ever.
Once you have had your 3 attempts you then have to go to a CAA Examination Centre to take any further papers, you can't take them at your flying school. As the CAA will have to write any additional papers after the 4th attempt, you may have a very long wait.