My son is now in year 7 at a local independent school. He leaves the house at 7.45, walks 20 minutes to school, to be there in time for an 8.15 start.
School finishes at 4, and he is home for 4.30, if he has no clubs or games after. He has clubs twice a week, and then he can leave school at 5.30, so he is home for 6 pm. Even without the nightmare journey you plan for your son, he is tired. It is a long day at school, with many new subjects, and complicated homework which is very different to the type of homework he had in primary.
I think you should focus your efforts on looking into moving nearer the school instead of searching for information about transport, if you are serious about wanting Tiffin for your son.
You dont want to ruin your childs educational experience and his zest for learning by making him put up with this journey.
Incidentally we turned down a good (Catholic) school not far from you, due to distance.