I think that a significant part of the reason why 9 out of 10 of the most over crowded bus routes are in the Southeast and 5 of them serve Lewisham is ironically because of good planning rather than bad. Lewisham have worked with TfL for years to put more services into more areas in more appropriate ways and one result of that has been increased ridership on buses as the services have become rapidly more popular.

Generally there is little opportunity to increase the capacity on a route except when the route is retendered ( although it can be done, it is more tricky and tends to cost more if the capacity is increased mid-contract ).