Hi guys. Appreciate your thoughts, I really wan't too sure where to start once my interest was piqued. I probably should have posted this other frame at the outside. This is the preceding 200sec Lum image which has caught the end of the object moving up from bottom right. These were both unbinned images, so the absolute fastest time the camera could have start with first image I posted would have been about 20 secs. The FOV is about 60 arcmins wide (FL 1000mm) so I was surprised a plane would be travelling that slowly even at very high altitude.
Anyway, I've learned something - didn't realise geosync satellites could potentially be seen so late.