What I am reacting to is a PP who said that as long as their child got into sixth form, their GCSEs don't matter - as if they start with a clean slate.
Well, reality is that they don't. Their GCSE results stay with them, even through to job applications after their degree.
When they do their UCAS applications, just over a year after getting their GCSE results, the only qualifications the universities have to go on are their GCSEs. They may have AS module results, but these tend to be at the bottom of the heap when it comes to evaluating the application, after GCSE grades, predicted grades, personal statement and teacher reference.
Obviously, there is no going back now on their GCSE grades, so if they have Bs and Cs, they need to be thinking about how to strengthen their UCAS personal statements, and also to be very strategic about which universities to put on their application forms (and to listen to sage advice).
The PP who mentioned being successful in clearing - well this is a completely different kettle of fish, because it is based on actual A level results rather than GCSE-reinforced predictions.
The PP who was hoping that grades would improve at A-level. This is very unusual. You would not give a predicted grade of an A for a pupil who got a B at GCSE unless they were a particularly late developer or who had extenuating circumstances. For these pupils, there is always the option of applying a year later when actual GCE results are known, and to do a gap year.