I am not sure when the induction day is but in the past they have also run a series of after school sessions for girls about to start year 7. They played rounders and had fun. My DD was going to RH by herself and enjoyed these so I would recommend doing these if they are on offer again. A good chance to get to know other girls.
There is a pool and DD did have swimming in Y7 but hasn't done that much swimming at school since (there might be a club though?).
Uniform can be bought/ordered from the school uniform shop in Gloucester (oops, can't remember the name!) I would recommend going for the cotton jumper, the poly one gets full of static!! You can buy leotards and dance wear from dancedirect or I think, order them at the eve induction meeting for parents. I am sure there are second hand uniform sales at school but you might need to give the school a ring for when the next one is. Possibly at that eve meeting??
As for a school bag.....let's not go there!!!