Sure, I wouldn't expect your average 24-year-old developer to be getting to top rates unless they have an especially good reputation (more for contract work, admittedly). However, London IT salaries are high, and software development is, IME, pretty meritocratic. Although job adverts often ask for years of experience (on more than one occasion, I've seen adverts asking for 5 years' experience in a technology that's been around for less than 3), I know I've never been properly qualified for any job I've got.

Just a quick search on Jobserve brings lead developer roles in London varying from £40k to £110k on the front page. The latter is asking for 5 years' banking development experience.

To be honest, though, you can live very well in London at the lower end of the salary range. Frankly, most people do well off less. But IT is a pretty well paid industry in this city!