Probably early, and we were always sent back to our rooms until at least 7am. Stocking presents were designed to keep us occupied and we were legit allowed to eat the sweets and fruit in them, usually there was a book and a game or one of those little puzzles to take apart.
I'm not sure it was ever explicitly stated but we never ever opened under the tree presents until after breakfast and our parents handed them out one by one, we took turns to open, so that we registered what we had (in our heads) and it wasn't a free for all so that we forgot what we'd been given. If it all got too hectic, we had a break for a game or to play with the things we'd already opened.
No presents (except stockings) until after breakfast was eaten and washing up done. A tradition we still have now which is great.