RG is just a daft marketing term thought up by a bunch of Uni who felt threatened by the 'new' ex-Poly Unis in 1994.
Plenty of Unis who anyone would regard as a 'top Uni' are not members of RG - Bath, St Andrews, Lancaster for starters - and this actually shows you how daft the whole 'RG' thing is.
Bath is an amazing Uni, and certainly on a par with Warwick. You like the Uni, you like the course - then that really is what matters.
Enjoy Bath - you'll have a fabulous 3 years.