This looks really promising - I was wondering whether there would be any chance on a tutorial/step-by-step guide on the basics?

I've just had a go but I'm struggling with the fundamentals using the GUI to convert - for example I can't successfully convert a head .o model to GLTF and import to blender (also can't do the reverse - when converting a .obj file exported from blender to .o file type I get a invalid mesh/corrupted error message or 'Not a valid .O file!' error message when trying to view the head model in oedit).

Were you able to test any edits to the models in game?