Hi Nick,
Yes, I know what you mean, there's nothing like a big transmitter hall with the roar of the valves was being cooled like the engine room of a ship! The new TX's are just a box in the corner of the room.
No, you don't need to take the exam again, things are changing quite a lot as regards the licensing structure in the UK, I think the Morse requirement will probably cease in a year or so. I am not sure how you stand with your exam, you may well find that you could get a class "B' call and when the Morse is dispensed with, you will probably move straight on to the class "A' call with the big boys and their toys.
Have a look at the Radio Society of Great Britain website, maybe send them an email and ask what the position is.
Radio Society of Great Britain Let me know how you get on.
Paul.