Deceptively hard to answer. * Cost of living varies a lot. * London is kind of a country in its own right. * Commuting in the UK can be £5k or more.

If you compare to the national average salary for full-time employees (which is around £32k) then most programmers are well paid.

See also http://news.bbc.co.uk/1/hi/8151355.stm "What is a big salary"

For a startup in London an intermediate level developer can make around £30-£50k, more senior developers can earn more.

In sectors like consultancy and finance salaries can go into the £70-£100k range.

And there a bunch of sectors like gaming which fall in between the two ranges.