So, my PCs are just working their way in to Thistletop at the moment. They have got through the Thistle maze and had a pitched battle at the doors of the keep. Then, victorious but bloodied they climbed up and into one of the towers, closed the trapdoor leading down into the building and hunkered down to rest and recover.
Unfortunately for them, I am pretty certain that every single goblin in the place is aware of their presence. One of the party members is a Cavalier of the Musketeer archetype, so every combat is punctuated by gunfire. The druid therefore knew about them in plenty of time to get off a warning sparrow and then the battle at the doors made sufficient noise to ensure that everyone else was aware of them as well. Added to that, they wounded and drove off the two goblins in the tower rather than killing them, so they are doubtless downstairs telling a story of attacking hordes by the time the PCs get into the tower and shut the trapdoor.
So I guess my question is, what do the goblins do at this point? Mounting a counter-attack sort of makes sense, but I am pretty sure the party doesn't have the resources (spells etc) to fight off the entire remaining population of goblins and I don't want to engineer a TPK. On the other hand, the idea of the goblins just doing nothing for 8 hours makes no sense at all.