CHUWI Hi8 CWI509

I have just acquired a CHUWI Hi8 CWI509. S/N is Q32G22160601996.
I can see the required downloads for other models, e.g. 1605.
I boot into Android 4.4.4 but cannot get to Windows.
If possible I would like to do a clean rebuild with both Windows 10 and Android 5.1.
Which set of files will I need?
Many thanks