I arranged for some dialect coaching, since the director wants Dame Carruthers to sound English and I know I need "professional help" to pull that off convincingly. Fortunately, I know a professional actor through church who, conveniently enough, is not only English herself but has taught dialect classes. She gave me several very useful "substitutions", as she called them, that will get me a long way toward my goal of sounding authentically English. I think the various "o" sounds will present the biggest challenge, but I've got time to get this down. She's even offered to listen to how I sound once we get into the theater, when the acoustics will change dramatically and affect how I need to produce my sound.
As I told her, all those years I spent sitting in foreign language classes, trying to master the pronunciation so I don't sound so American, are continuing to pay off.