You're right - Durham is beautiful, and, if I've been informed correctly, Warwick falls off the other end of the scale! One of the advantages of Durham is that you live in a cathedral city (some of the sunsets have to be seen to be believed), but have Newcastle (which in my humble opinion is better than Coventry) only 15/20 mins away by train for serious nightlife/ shopping etc.
You say you also like the collegiate structure - this will give you a lot more out of uni than others (apart obviously from Oxbridge). There's a strong sense of belonging which you don't get in most other unis, and this encourages a lot of students at Durham to get involved in the JCRs/ sports teams etc. And even if you don't, you still get to reap all the benefits - not only are there Uni-wide events, but your own college ones.
I don't honestly know much about the Philosophy dept. here at Durham as opposed to at Warwick but of the guys I know doing Philosophy (prob. about 7 or 8) they all love it. If you do a straight Philosophy degree you can do two other modules in another dept. I think and if you want to do Pre-Socratic Philosophy or Aristotle and Plato in depth, there are a few courses in the Classics dept. that I'm doing and the lecturer is absolutely amazing (sorry for that digression, but I'm realyl enjoying my course!). I do know that the DUNELM part of your degree will look good on your CV when applying for jobs.
Essentially you've got to ask if you'd like to study at a university where you don't feel inspired and that you don't find attractive but will get what you think is a better degree, or study at Durham which is one of the most beautiful cities in England, will inspire you and make you happy, and give you a degree that might not be so 'academically credible' but you'll have had fun studying for.