I found it easier to explain to the sales exec that you would like 15 minutes alone with the car. Tell them you’ll let them know when you’ve finished looking and get them to leave you alone.
Take your time looking over paint, check the seats for any marks, scratches on the media display. It sounds a bit daft in a brand new vehicle but you’d be surprised just how many vehicles are not PDI’d properly! Ask your sales person to check the fluid levels before your drive off too, my oil and coolant were not topped up as the PDI would have them do, coolant was below minimum on a brand new car.
Otherwise, enjoy it, but please, please take those 15 minutes you’ll be glad you did if you discover something later.