After following the steps above it seems to be working for me. Many thanks for your help.
The model does seem to be less stable with even a simple imported building, I have had a lot of crashes.
The last attempt went well, a useful tool I found is the SketchUp extension SolidInspector2. I had been trying in vain for a long time to fix my buiding to have volume. I installed the extension, hit the button and it fixed it instantly.
Thanks for your efforts on the great new feature. Keep up the good work.