My local dealership isn't the biggest, but I think they can fit 8 MINI's inside (off the top my head) and is built on the same land as the BMW showroom, sadly the parts and workshop etc are in the BMW Showroom.
Where they were before (above is a new build) MINI was like an add on to the build and looked very cheap because the roof was showing etc, and was only big enough for 4 MINI's.