Yes there is a package awaiting DS when he gets up(!) labelled UCAS/Gillette so I can assume he has received the same today!
The main reason that schools are not telling students/parents the centre assessed results is so that there is no wittering on about wht X got higher than B and so on, and so that there can be no parental pressure placed on those calculating the grades.
Please also remember that the grades are not just based on the mocks but also y 12 exams, in class tests, homework and so on. Therefore if you child is usually a high performer or at the top end of the class then feasibly their grades will be anyway.
After results the school can tell your 18 year old (but not you unless your 18 year old gives permission) what grade they had calculated and this may be helpful in deciding whether to sit the Autumn exams. My understanding is that they are not allowed to tell you the ranking as that could lead to giving information about other pupils in that you can work out where others were ranked based on your ranking and it therefore falls within the exemptions for subject access requests.