Just to help anyone having same issues i was, so to start short back story on how my issue occurred:
Got used to unity's acceptance of laziness
, basically in blender, without UV mapping I could assign materials to different faces without having to texture properly and it would just work in unity. I then tried to bring these models into GG......... well many fails later I found a way.
Basically have to remove all assigned materials, generate a UV map and then it works. However you can still use the materials to generate your diffuse map. Simply go to blender render mode, generate a UV map, bake texture to a new image, save that image as a .png, then delete all materials and export as fbx. This then works with the importer.
Anyway I imagine select few will have this fault but hey thought I'd share regardless. And it is a very easy way to create your diffuse map for simple colored items. May share a video on it when i get more time. Anyway quick screen of some models done this way very very quickly and without any normals or specular maps generated / made yet.
PC Specs: Windows 10 Pro, gtx 1060 6Gb, 16gb DDR4 2400MHZ, SSD, i7 7700k liquid cooled, ASUS Prime motherboard.