We received our invites to SPGS and NLCS interviews today. Does anyone have any tips on these interviews? What format do they follow and what sort of questions do they ask?

At NLCS my tips are:
Eat the biscuits. It helps with nerves- yours and DD's
The interviewing teachers are really lovely and just want to know how your DD thinks. You can't prep for it.
Nobody cares what you or DD wear.
No one will interview parents.
If you haven't discussed bursaries in advance, you can ask on the day and you'll be walked over to the Bursar while DD is distracted with another tour.
Take advantage of parent helpers and ask questions.
If you stay relaxed, DD might as well.