this seems to be yet another area of confusion, does anyone have the definitive answer - can you train people who own/part own a non EASA (ie. permit) aircraft for EASA licences/ratings?

Can you train someone for the issue of a licence or rating on their owned or part-owned permit aircraft? Well, the legal answer is yes, but I suspect that the practical answer is probably not. The snag is that, understandably, all such training needs to be done at a training organisation (ATO/DTO/RTF - whatever they need to be these days). That means that the aircraft in question needs to be ‘on their books’. They need to take responsibility for the suitability of the aircraft, its safety, oversight of its maintenance, the way it is operated and probably more.
A chap whose aircraft shared a hangar with mine had a long-lapsed PPL and, as a favour, I asked the owner of the flying club where I do some instructing if I could use the umbrella of the club to retrain him on his permit aircraft. He politely declined and his point was that it was a lot of hassle for him in return for minimal return, basically just his slice of the instructor fee. Actually, he didn’t politely decline it, he said “I wouldn’t touch it with a ****ing bargepole”.
Other opinions are available, I’m sure.

http://www.lightaircraftassociation....20Aircraft.pdf

Thanks, I knew there was that TL but had not chance to look it up,

We are actually coming at this from the other side as a DTO that would be offering this to people, we already have one aircraft on our DTO and may be offering 1/20 training shares! Plus offering training for others who have their own aircraft.

Not sure how big the market is, but if you can do this and maybe remotely oversee training away from your home base, it’ll be a winner.