Not the best cyclist (Only got a bike last year!), and as I live in suburban London, don't really cycle outside of it. Usually my ride (don't often have hours and hours to spare) involves going down to Chiswick Bridge, before joining onto the Thames Path, and cycling up by the Thames through Hammersmith Bridge to Putney Bridge, then taking a few moments to get a sip of water at the bus stands at Putney Bridge, (also to admire Abellio's Dennis Dart 8037 as a meal relief bus for drivers

) before either going back the way I came or taking a ride through Putney and Barnes on the south side of the river. Another route I also do if I have more time is to go straight to Putney Bridge, before using the back roads to get to Fulham/Chelsea, then using the cycle lanes up to South Kensington, through Hyde Park and all the way down Oxford Street, Theobalds Road & Clerkenwell Road to Old Street before turning around by going through Pentonville & Marylebone, back down through Hyde Park, South Kensington and through Fulham.
Recommend going on this cycle, which I recently did. A nice route by going straight up through Putney Bridge & Fulham/Chelsea to South Kensington before going down West Cromwell Road to Hammersmith (partially on road and partially on pavement which I think was designated for cyclists as well anyways?), then down the Thames Path to Chiswick Bridge, along the cycle lane by Lower Richmond Road to Richmond, down Petersham Road/Richmond Road to Kingston, up Coombe Lane to just past the A3, then up Copse Hill to Wimbledon Common, through Wimbledon Common & Putney Heath home. Good mix of residential & main roads as well as some cycle lanes/routes and parks. 26 miles which I think was fairly good, considering I'm still new to it and my bike is stuck in 2nd gear

(lol, haven't had the time to go to Halfords and get it fixed yet ; really need to do so soon as I broke down on a blind corner on a gradient yesterday! Luckily the car behind was slowing down to turn anyways so nasty incident avoided, phew!)
Few things that annoy me
-No matter how hard you indicate turning right with plenty of time, no car drivers seem to realise you're there until the very last moment.
-People being oblivious that they are walking on a cycle route when the pedestrian path is clear
-Car drivers not giving enough room whilst overtaking
-Others cycling way too fast on a cycle path (such as right next to the river) , especially if it's a time when lots of walkers are around, so they swerve around them and nearly into you on the other side
Though at the same time it is also positive
-Beautiful views, especially where some may not be reachable by car/bus etc.
-Good for the environment

-Healthy and relaxing
-On a bike, it's much easier to change plans to go after specific trains/buses rather than in a car or on a bus