I’m sorry , I’m probably going to cause an upset but
Party starts at 7, ok but who arrives at 7 ?, I would arrive 7-30 / 8 so in my book 8.15 ok a little late but still ok.
Tables/chairs again , sorry, but surely you provide seating for everyone? The only place I would question is a bar/pub location, but even then people would want to sit when eating. Which brings me to food, party starts at 7 so food would be 8 ? And surely people would take a good hour eating ? And to run out, that’s the biggest no, I would die of shame.
So basically, party starts at 7, arriving at 9,15 I would except getting the remains of buffet, but 8.15 the party should be warming up and people starting their meals.