I like to think that Much & Robin’s attitudes toward each other in Ep1 are consequent of the MONTHS long journey home, and the fact that while on earlier parts of it (such as on the ship) they were around other people, the last part of their journey it’s just been THEM.
So, like a cross-country car trip with just one other person. And you are both getting on each other’s last nerve, and Much wants to sing along with every 1D song on the radio, and the way Robin chews his food is starting to drive Much insane, and Robin keeps slowing them down by flirting and trying to hook up with every pretty girl in sight, and nothing they’re seeing is good enough for Much (not the views, not the food, not the landscape) because it isn’t LOCKSLEY…
…and well, notice the entire change in Robin once they get to Locksley and Much is in the bath (alone) and Robin walks in, and suddenly they’re on much better terms
…and they just needed a moment’s break from each other.