Ok! I did this after a test game against Rotwang who gave me some really useful comments.
Put double doors to the side of metal boxes to stop camping plus allow larger units to enter. Only one entrance/exit. Plus the whole room is smaller and not split up.
Broke up force fields as they were too Grey friendly. Plus took away a few pieces of the henge to allow missile paths.
I think I still need to work a bit more on floor tiles. Anymore suggestions?