Beauty is in the eye of the beholder, and I'm a firm believer that, in education, one size does not equally fit all.
For you, it sounds like being surrounded by students having similar focus/priority/achievement with respect to academics is important. If that's a big part of your definition of what constitutes a "better" university, then it's not necessarily "egotistical to say that [you] feel [you] could go somewhere better with [your] grades." For example, if you have an unconditional at Durham, which has an average entry tariff of 185, it is statistically "better" in view of a factor important to you than Nottingham, which has an average entry tariff of 155. (This is true also for Bath and Warwick, which have average entry tariffs of 180 and 179, respectively.). Personally, I don't see anything wrong with wanting an educational environment that better matches what you were hoping to find, and which may be a better overall fit for you. If anything, I think you just fell victim to the great marketing that RG has done (and/or the global league tables, which focus primarily on postgrad+ level research, as opposed to factors that may be of more interest to, and more directly affect, undergraduates), which may have led you and/or adults advising you to assume (incorrectly, as you have discovered) that RG universities necessarily have, on average, the students who were the most academically accomplished per A-level results.
All of that said, I'm sure you could obtain a fine education at any of these universities. Whatever you choose (or have presumably chosen by now), best of luck.