Well I never ...
Interesting Wikipedia Article on RN "Fleet Tenders" which in fact were three dummy battleships (HMS Resolution, HMS Revenge and HMS Anson) and an aircraft carriers (HMS Hermes):
I had heard about HMS Centurion pretending to be HMS Anson in the Mediterranean however teh others I knew nothing about! The only other "dummy" battleship was the WWI fake HMS Audacious which was faked after the real battleship foundered on a mine in the early days of the war.
I followed this thought up to the following link (apparently there were 14 mock WWI RN Battleships: