Nice post, James.. to follow up a little on this comment:
Don't let his or her presence stop you from inspecting or testing anything that would not damage the boat. Ask if you have any doubts about whether something will damage the boat.
One of the easy things to do as a pre survey inspection is to look for serious, obvious voids and delam in the deck. A simple tap test will do it, you'll quickly here a dull/hollow thud as opposed to a sharp tap when you move from solid laminate/core to separated. Be aware that on top of bulkheads and other solid reinforcement the 'sound' will change too.
But you don't want to whip out a 5 ib ball peen hammer for this..
... one of the handiest tools for this is a stubby screwdriver, used upside down as tap tester. It's small and fits easily into any pocket, and doesn't appear threatening or 'dangerous' to the seller.
Also don't wear soft, bouncy soled shoes.. (like the 'air' soles some sell).. that can feel like bouncy decks underfoot.