I had not realised the 30% issue.

What do you mean by "30% issue"?

Under Windows, the imported stuff isn't stored at the same place in the free version and the paid version, but I experienced that what you imported in the free version was available in the paid version. Maybe it wasn't your case.
Could you check the content of the folder C:\Users\user\AppData\Roaming\eTeks\Sweet Home 3D (where user is your login)? If it contains some .pref files and a preferences.xml file, you should try to copy them to the folder C:\Users\user\AppData\Local\Packages\eTeks.SweetHome3D_y7v7etvrysvmm\LocalCache\Roaming\eTeks\Sweet Home 3D\
Hope this will work...