With all due respect, but how in Zeus' butt-hole, did the following thought manage to rummage its way through your head: Ok, I am a good, determined, motivated student, I have been predicted 3As at a-levels, should I apply to the Oxbridges, LSEs, Kings, UCLs of this world and blindfoldedly shadow the herd, or should I follow an (indubitably) virgin path and go to the University of Gloucestershire? Uhm, yeah, I'm a maverick, I'm a true unconventional, anti-conformist revolutionary, I'll take Gloucestershire any time ?? Apart from anything, didn't the fact that the entrance requirements at "glos" are CC kindle some sort of (un)conscious irritation -- uhm, perhaps, and this is merely a far-fetched conjecture, I'm slightly better than this
To be fair, and please take my previous comments with a humorous pinch of salt, it does depend on what sort of legal (or any other) career you wish to pursue. If you are not that keen on the glamorous slavery imposed by Magic Circle firms (or any other relatively large city practice) and are determined to open your own high-street niche practice, then, of course, it doesn't matter if your LL.B is from the University of Timbuktu (which, in all probability, is better than Gloucestershire), nor does it matter whether you got 100 firsts and the Clifford Chance award for memorising academics' names better than the rest of the class.
However, the tone of your post suggests that you have other inspirations, perhaps more closely linked to the aforementioned submission to those soulless city monstrosities. In which case, then, I strongly recommend you take a nice gap-year, indulge in some obscure charitable enterprise that might look vaguely impressive on your CV -- such as "I was project-leader in "Save the Mice" London Underground operation -- and then re-apply, provided that you have the requisite grades, to top-tier faculties.
To convince you further, even amidst the contemporary championing of egalitarian recruitment policies, law firms (and all other major employers) expressly state that they won't "discriminate" against you provided you come from a "red brick" university. Uhm, already there the chances of Gloucestershire proud alumni are frighteningly slashed. Also, bare in mind that Oxbridge, as you rightly pointed out, is still, by far, the prime recruiting ground for City firms -- talking to the Herbert Smith graduate recruitment buffoons, they shamelessly confirmed that 50% of their intake is from Oxbridge. These absurd proportions are reflected in all other law firms -- hence, it wouldn't be an entirely wasteful exercise to send that application to Trinity College after all.
To pick up the pieces of whatever is left after Oxbridge, are all the other traditional institutions, with the big London ones (UCL, LSE and KCL) and a handful of others (Bristol, Warwick, Manchester etc.) ahead of the rest of the pack.
That said, it is of the utmost importance that, even if you are fortunate enough to be get into Oxbridge or any other well-respected institution, you get the grades. If you end up with a 2:2, in the vast majority of cases, they'll chuck your application in the bin, regardless of whether your tutor at Cambridge was Bob Hepple QC Ph.D FBA CBE or whether during your fruitless time at the LSE, you heard Carlos The Jackal speak and your christmas bash was sponsored by Linklaters.
Indeed, in some exceptional circumstances, equally exceptional performance at university may actually tilt the scales in your favour, regardless of how ill-reputed your institution may be. However, I'm talking about first-of-the-year sort of thing. At a reception at Slaughter & May (out of all places), I spoke with one trainee from Northumbria University-- not exactly G5-- who had no trouble getting in the mother of all conservative law firms. Further inquiries uncovered that the reason for this admittedly miraculous occurrence is that he had obtained, by far, the best overall performance in the class -- indeed, I think in the entire history of the (relatively young) Northumbria law faculty.
So, unless you think you are capable of that sort of performance, I vividly recommend you re-apply to a traditional university, with a traditional LL.B. Indeed, if you actually get AAA, then you should definitely apply to a top ten place (as if there was an established top ten – in any case, a place with a AAA offer) and, more importantly, you should give a shot at Oxford or Cambridge if you can.