I'm a first year PPE student here at UCL and like you last year I struggled to decide between UCL and Warwick! Here is what I think:
1) London is generally expensive for housing, but if you're able to afford the prices of UCL accommodation, then don't worry as you will easily find a flat
2) don't worry at all about making new friends, it's normal to start a new life and at first, it may be difficult to adapt... but trust me, there are tons of opportunities to get on with people
3) London is amazing and very stimulating, there are a lot of events that you can attend (also for you that study English)
4)UCL is internationally more recognised than Warwick and its English department is one of the best in the UK
5) Yes, it is a very tough uni, I don't know for English, but at PPE we study A LOT and for a lot I mean A LOT ahah but you can have a good social life
This is what I think. However, Warwick is a very good choice and you're not gonna ruin your life by going there!
At the end of the day it's your decision. Take into account if you would like to stay in a big city rather than a campus. For example, I came from a little town and the idea of being stuck in Coventry wasn't very appealing.. but again it depends on you
let me know if you have more questions