A little update from this, Owner has recently seen his premium go up massively with a claim of 5,000, still going down the insurance route but after informing him I've seeked advice/suggestions (not just here) he has changed his views.
Now says me having his vehicle at any point were lent out on a "friends" basis and he doesn't hire his vehicles out. Surely this cannot be correct with someone performing a trade and still has our vehicle that still needs a major repair and it's been months with delay after delay?
Also says he finally spoke to the person on the phone (the contact details given to me during the accident) and they the company are now saying it has been returned to the hired company and written off with the garage owner taking the blame on his trade insurance.
I've said I would co operate in explaining and providing a statement/pictures as I feel I am not 100% at fault but he seems enraged with him taking zero responsibility in providing his own vehicle correctly to his customers.