Gatwick is the perfect airport if you're going to South London.
- You can have a shower for free (or for £1 if you need a towel)
- Visiting London for a while? You can buy a local SIM card for your mobile from a vending machine next to the toilet on the first floor, near arrivals.
-Gatwick Express: Takes 25% less time, Costs 120% more! (Southern Rail is a better option unless you're in a great hurry).