[Tracy34]

In 'the guide to filling in your passport' booklet it says

Adult tick box, RENEWAL
put a cross in this box if you are 16 or over or if you are a child who is likely to become 16 before we issue your new passport and you have a fully valid passport which, you want to renew, is not damaged, does not need to have any details changed.

In this case fill in sections 2,3,and 9.
You don't need the photos countersigned unless your appearance has changed.

You don't need an interview unless you have never had a passport before, and this is your first application.

Adult replacement means if your passport has been damaged, lost or stolen.