The B.P.F. or British Pacific Fleet had 4 active fleet carriers under the command of Admiral Spruance, C in C of the 5th Fleet during the middle of march '45. Since the BPF's escorts and battleships were slower than that of their carriers they were restricted to lesser operations, for instance, during the attack on Okinawa the 5th fleet directly supported the landings on the island while the BPF attacked airfields to the south of Okinawa on Skashima which the Japanese used as aircraft staging points.
Indefatigable, Illustrious, Indomitable, Victorious were the 4 HMS on station, April 20th the Illustrious was replaced by the Formidable, due for a refit and its aircrew's required tour of duty long past.
True the British had armored Flight decks but they also couldn't carry as much aircraft as the US carriers, 34 originally untill they were upgraded to 74.