It looks like the only effect the lock down is having for year 12s is that you won't have lessons or mock exams at the end of the year
There's not really a thing such as "Resitting year 12" because there arent any official exams for year 12. Predicted grades will most likely be decided via a mock exam when you go back in september (as your school submits your predicted grades around november/december).
And as for personal statements, most people start writing theirs around september/november anyway. Only thing now is that you probably won't be able to get work experience to talk about in your personal statement, so you'll have to rely on previous work experiences to talk about in your personal statement.
So all-in-all, lockdown hasn't really affected year 12s at all
Possibly try to help out the NHS somehow? Everyone is going to talk about coronavirus probably in their personal statements so to stand out you could mention that you volunteered somewhere. That would be nice
But in general, I would definitely not stress about uni applications whatsoever if I were you. If you were applying to dentistry / medicine then maybe you have a case to be mildly concerned but there are still alternatives to hospital work experiences. (virtual work experience mentioned in this thread https://examqa.com/forum/discussions/medicine/#post-2530)