Well at Christmas time, as with many festivals, it seems to me you have to go with the flow to a certain extent. Even if you're super organised and arrange things early, you're going to encounter busy shoppers and pick up the sense of bustle.
Tim said "Enjoy the rest of the summer, boys; I know there isn't much of it left". I agree with you that the Christmas scene might not have originated with Tim; it might have come from ITV, and often he must have been balancing the competing needs of novelty, budget and audience taste. The implementation of his ideas, too, would have been through the personalities of the production crew, actors and actresses.
I remember being impressed that they had managed to source the evergreen in August; perhaps August wasn't the onslaught that it has become these days regarding the arrival of Christmas stock!
Isn't it kind of strange that the warmest month - August - is followed only four months (and not something like six months) by the darkest? Projecting forward - the deadest (December again) is followed four months by the liveliest, with Spring in full activity.