Formal:
* Vous habitez à Londres. (This is the most common and neutral way to say it.)
Informal:
* Tu habites à Londres. (This is used when speaking to someone you know well, like a friend or family member.)
You could also use the verb "résider" for a more formal and literary tone:
* Vous résidez à Londres.
No matter which option you choose, make sure to pronounce "Londres" with the correct accent: Lon-dr'.