The other option to get into the city from this neck of the woods is to take the train from Nunhead, Peckham Rye or Denmark Hill depending on your location, which stops at Blackfriars, City Thameslink, Farringdon & Kings Cross St. Pancras. The journey is 23mins from Nunhead to St Pancras, so shorter than that if you are getting on/off at any of the other stations. This is the line that runs out to Sevenoaks and used to terminate at Blackfriars, but since they are doing a lot of work there (with the new bridge link across the river meaning access from the north and south banks) the route has been extended north all the way to Luton & Bedford depending on which train you get. Its a very handy line, which I take now all the way to Kings Cross rather than changing at London Bridge and I avoid the tube altogether!