Thanks for all the comments
Well the stone masons are largely finished on the first phase - just the plasterers then decorators to come in. I finished off the walls and crenelations using a little jig I made up to get the 22.5 deg cuts. It wasn't perfect but good enough. Next is more filling, then painting.
Some example castles:



I am quite pleased with the range of options available and the way it goes together. Some neatening of the edges required to give a better fit but mission accomplished. I have some doors to make up that will drop in at required locations for access to the walls from the towers plus the trap doors for access to the roofs.
My plan is to use it in a siege scenario for Dragon Rampant with some home brew siege rules.