Huge fleet of bikes available for "hire" online. Mountain bikes cost 5Ps/hr, 28Ps/day or 75Ps/week. Road Hybrids (road tires and mountain bike flat handlebar) cost 5P/hr, 28P/day or 75P/week. Tandems, hybrids and others available as well.
London Bicycle also runs city tours by bike, so check them out if that interests you. The nearest Underground station is Southwark and the shop is close to Waterloo East, Blackfriars and Waterloo Mainline stations.
April-October: 9.30am - 6pm
November-March: 10am - 4pm