No, waste of time and probably not possible anyway due to timetabling issues with your uni exams.
Ultimately the grad schemes etc that care about your A-level grades are also likely to care whether they were at first sitting or resits anyway. The vast majority which don't care about your A-level grades therefore won't care if you got higher grades after a resit or not.
Anyway it's really a non-starter because there is fundamentally no mechanism to resolve clashes between your uni exams and A-level resit exams. Also you can't just "not declare" the resits in most situations later so you may well be in a situation where you have e.g. a B in the original sitting then a U in the retake because you couldn't go to that exam because you had an exam for your degree the same day. Or worse, you go to the resit and then fail a module on your degree...
That's even before considering the workload issues. Just not even worth considering. Far better ways to spend your time, especially in terms of improving employability.
Also I've moved your thread to uni life, as it was in the medical schools forum for some reason.