I will do as Hali does and tell people he doesn't like being humped and will warn their dog off if they don't keep an eye and make sure their dog isn't able to annoy Ollie.
I think all sides have a responsibility me to let Ollie tell them off but to make sure he doesn't go overboard and them to make sure if Ollie shows he is unhappy to call their dog off and move on which has so far happened. Their is always one idiot out there though and I hope I don't meet them.
Thankyou for all the comments I feel a lot happier about letting him have his say if he needs too within reason.