I'm also starting to consider how I want to run the campaign outside of the dungeon. So far both groups that have ventured into the dungeons beneath Nightwick Abbey have spent very little time in town. This usually consists of buying supplies and hiring hirelings. I'm fine with this, but such activity can't sustain a campaign for very long.
My current idea is to have the world creep in on them. Have NPCs make themselves known as they hear about the party's adventures. Present mysteries within the dungeon that can only be solved by talking to people in the village. That sort of thing.
If you play in my campaign stop reading now.
Ultimately I'm going to stick to the Basic/Expert divide and allow them to spend their first three levels mostly in the dungeon. I'm going to have the entrance to the fourth level of Nightwick Abbey sealed off with some strange, magical sigils. The party will have to travel to a city with a library or some similar thing in order to figure out how to open them. This will, I hope, cause them to interact with the world outside the dungeon but still keep the dungeon as the focus of the game.
Eventually I hope to get into the Companion rules for BECMI D&D and let them build their strongholds and manage them and what not, but that is a long way off.
Nightwick Abbey is the focus of the campaign, but it is a tent pole and what use is a tent pole without a tent?