Been through this twice as well.
Agree that extra curricular should only be small amount & related to relevant skills.
Work experience only stressed if directly relevant othewise included briefly with extra curricular.
The autumn term gets very hectic in y13 especially if doing course work or Jan modules so if DCs are in a position to draft PS then def. good idea. LIkely to be revised at least 4 times
Can also start filling in UCAS application on line. Lots of basic info required which they can start now & then AS results in August. Saves time once pressures of A2 kick in later.
Also worth noting that even if not applying for Oxbridge/Vet/Medicine/Dentistry its worth getting UCAS application in early as many other Universities will start interviewing/offering straight away & if its a tough year could be good to get in early!