Nurse,
Don't forget that Navy Days are effectively an "open day" that utilises existing assets to showcase the Navy. The Reds etc are "display" teams who's sole reason for being is to give a nice show to the public. Having been involved in open days at Plymouth in the past, I can tell you that the next day after the public had gone and we had skirmished the jetty, we were off doing fishery protection for a month.
Attractions like the RN parachute team are all volunteers who give up their free time to attend events promoting the Navy.
Cheers