I'm thinking the upper crust would have carried on this traditions of morning weddings. The well-to-do would be eager to preserve traditions, especially in the face of so much social uncertainty. And really, Wodehouse's world was untouched by war, so having his circle of friends and enemies adhere to the morning-wedding tradition would not be far-fetched.

In the last Jooster episode, it appears to be a morning wedding. Bertie is wearing gray, which was considered a morning color, I do believe. I would think that you'd be safe in keeping the tradition of a wedding in the ack emma.