to echo the above , take snacks ( granola bars) that kind of thing. If your test is delayed , you need something to keep the blood sugar up.
I don't know how the ground portion works in the UK but I made sure that I had all the paperwork / documents ( weather printouts/weight and balance / log for XC etc.) in clearly labelled sections in my binder and had used index tabs on the relevant sections of the POH
that way I could instantly put my hand on the information he asked for and it makes you look organised, good impressions count!
Good luck
