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"