Yes, I ended up adding extra parts instead of beginning to paint it.
The front door of the restaurant was looking a little plain, and not very faux-oriental. So I built up the entrance with some more cut-up cardboard.
While waiting for that to dry, some more relief detail on the walls didn't seem like a bad idea, so more foam sheet was sliced to oblige.
Once that was on, the roof looked a bit big and flat, so a bunch of off-cuts became a landing pad. It didn't look very functional so it got some stairs. Then it looked inaccessible, so I built a roof stairwell. Then a pathway.
One interesting thing: When making to roof for the stairwell, I didn't have any card to hand of the thickness I wanted. I did have a little piece of styrene sheet though. Thinking a clean bend would look better than a seam, I tried to fold it around my steel ruler. It cracked.
After a think, I cut another piece.Went over to the hob/stove/cooktop (depending on where you live) and wrapped one end of the steel ruler in a tea towel to protect my hand, then heated the end over the flame. I then pushed the hot end of the steel ruler against where I wanted the bend to go and carefully applied pressure. It worked very well, and I'm now considering the many possibilities of formed styrene sheet to use alongside foam and card.