I go to KCL right now studying a different course but on the same campus as English lit students, and I did have to decide between KCL and Warwick when I got offers from both
I can give you the pros and cons of KCL itself and maybe someone else who studies at Warwick can also input
Pros: location - Strand is so close to all the good places in London such as Covent Garden, Oxford street and it's very accessible by tube if you're commuting. There's so many amazing cafes and restaurants in the area. The uni is quite diverse and the campus is really pretty too (huge plus for me!), lots and lots of opportunities available in terms of networking and careers and guest lecturers. There's so many events going on that I sometimes can't go to some because they're overlapping. Societies are quite fun and there's such a variety that you will probably find something you're interested in.
I currently love the modules I get to choose from for next year (course dependent) as there's a lot of variety and the option to take modules outside your department - so if you're studying English lit, you can still do a couple philosophy modules.
Cons: because Strand is so central, it gets so busy around campus especially as many offices are also located in the area and tourists during Christmas makes it much more busy. this also makes it harder to know a lot of people since once you leave campus, everyone goes their own way. Getting information is different to sixth form and this might not be specific to KCL but I always have to find info myself including important information about my course, study abroad information.
Advice - read about the modules that you might do and read around the topics. consider which location you'd prefer, Warwick is in a much quieter area and more campus like than Kings. for philosophy, I'd recommend reading around the topics if you're new to it and see if you enjoy reading about philosophers.
London is also expensive so if you're looking to get accom, I'd consider whether the extra costs is worth the experience, especially as accommodations aren't next to the uni campus, you'd have to take bus/tube typically unless you're at Stamford street (but I think that's just for 1st year). Tube can cost up to £25 a week from zone 2.
hope this helps !