I agree that the timing is a bit of a problem. Eating dinner before a 7pm social event, for many people, means eating early and fast. I know I rarely eat before 7pm, and to eat dinner, clean up afterwards, get ready and travel to the pub would mean eating by 5:30 at the latest. But at 7pm, I'd still be full from dinner, and not want to eat.
So for a 7pm party where light food is being served, I'd probably grab a light snack before leaving - a piece of fruit and some crackers, say, and plan on eating most of my meal in the snacks. My husband, on the other hand, would probably not eat before hand, but would plan on eating something after getting home later that night.
If I were meeting friends at the pub at 7pm for a normal evening, though, I'd eat dinner at the pub. So I wouldn't be too surprised if people at the event decide to order more food, to make up their dinner, as it doesn't make a whole lot of sense for someone to either go through a rushed dinner early, or go hungry until late, when they're going somewhere that sells meals.
In a situation like this, I might be tempted to go to the pub an hour early, so I can order and eat a light meal before the party starts, with a minimum of extra fuss.