Only in extreme cases is there such a thing as being too unrealistic (the old member ^mjg^ was a good example of this) but if you have the enthusiasm and the drive then just go for it! Although i would suggest that half of your six choices go to maybe first or second division universities which are really just as good and maybe only two or three for notts and bristol and such. All you really need is a great personal statement and reference which im sure you're more than capable of because you seem like you really want to do this. You may also need, for the more popular universities at least some decent GCSE grades. Most of all, please don't let anyone tell you that you're not good enough for these universities- just try it I'm sure you'll be surprised.
Oh and, not to be discouraging but if you can, try and change your a-level in law to something like history or geography or a science/language- if it's too late then don't worry about it though. And how come you opted for an AVCE instead of A-level? Not that it's bad, just wandering, you may have to double check that your chosen universities accept AVCE's.