3 of those unis I applied for and I've just firmed Leeds for Politics and Parliamentary Studies. ALL of them are good unis, lboro is my insurance because its a fantastic uni in itself with a great course and good rep.
My biggest piece of advice would definitely be to visit. If you're a really social person Warwick won't necessarily be for you as much as Bham or Notts would. You can only really truly get a good idea of a uni by visiting. I was adamant to make Sheffield one of my 5 but after visiting I absolutely HATED it and had to find somewhere else quickly! So don't be absolutely set on your options before you visit
Also make EXTRA sure you check out the modules! I applied for Bham and got an offer THEN checked out the modules and found it to be very economics based, which I despised the idea of, so that was one option out the window!