Don't get disheartened when you read these big salaries online. The average reader isn't bothering to post theirs.
The UK is actually pretty good when it comes to IT salaries. Go to France, for example, and they're much lower. The attitude to devs is quite poor in a lot of places, treating us like we're one rung above car mechanics. We also have a good contract market in the UK; in many other EU countries (even Australia) contractors make peanuts in comparison.
Outsourcing and the low barrier-to-entry have all dampened IT salaries. Immigration has also played a part in the UK over the last 15 years; a lot of devs from Eastern Europe have gone where the money is - i.e. here. I know it's a contentious issue here but I say that with no malice. I'd do it too if I was them, and a lot of them are talented devs, but there's no point pretending it hasn't had an impact.