I'm afraid ours all attend / have attended schools less than five miles from home, so whereas the journey time has never been less than one sixth of the time of the one that you are contemplating for your DS, the only time they have taken that long to get home is when stopping off somewhere on the way for social reasons.
I would certainly echo Twinkle's concerns (although if you really must send your DC 30-odd miles away for school, this looks -
on paper at least, to be one of the least complicated journeys I've looked at on here) - if you live in Croydon, you can't have been unaware of the industrial action which has caused so much disruption to passengers' lives in the recent past. Also, it is the parents' responsibility to get their DC to school in a timely manner. I have no experience of Skinners, but DD's previous school, although generally sympathetic when major transport failure occurred, made it very clear that, for example, difficulty of journey / distance would be no barrier to being given after school detention - and one of the reasons for getting one of those was a given number of unauthorised 'lates'

.