Was looking at Monday Knight productions and came accross a stable and tower for 25mm that might be of interest for swashbuckling encounters. Both of them have roofs that are removable. I've seen the interior of the tower before, and it is reasonably well detailed with a cobbled floor. Link:
http://www.mondayknight.com/index-Terrain25mm.htmThere is also a 20mm St Mere Eglise Church that might be useful, although there is no indication that there is a playable interior space.
Warren