Youngvisiter - I agree about the tea and sugar.
Does he annexe though? He is in a long line of racial others (Heathcliff, Dracula, Paddington) who are invited to cross the threshold.
Unlike the more dangerous characters in that line-up he also leaves at his own bidding: 'I think I'd better go now' and he went.
Like Paddington his comic force comes largely from his attempt to follow British conventions and his attempt to appear au fait with British manners.
He could of course destroy the tea table, but wants to sit there as an equal. He can't be as controlled and disciplined as his English friends but doesn't really notice that he is breaking lots of rules.
The purchase of the tin of tiger food puts him back in his place on this reading because, even if he comes back for tea, he will not get cakes and beer. He will get food that relegates him to the status of a racial other.
On the bulimia idea, most of the pictures show Sophie being affectionate towards him and so the focus is on him as a figure for her desire to eat everything on the tea table rather than the few bits she is allowed.
The carnivalesque reading works really well and accounts for that sense of relief and new appreciation of plain old daddy-centred home life at the end.