I understand what you say because I had huge trouble finding anything on it today.
Though I did stumble on a dancing amateur film which switched quite soon to the dancing in the streets. The Savoy part was so blurred that nobody was recognisable.

I think the official Coronation Ball was on 27 May at the Albert Hall.

I think Princess Margaret, and Princess Marie Louise, attended a ball in May, at the Savoy, with funds going to support docklands services.