I am a student who will be living abroad in London this fall, and was wondering what the most popular carrier was over there; I kept the same phone I used as when I was in Paris, and I just wanted to know what SIM card I should get for London. Just from some research online there seems to be a number of companies, Vodafone, Orange, O2 etc. As to rates and more importantly coverage, what seems to be the most reliable carrier? Any help is appreciated!