Although the pound has recently crashed, the general rule for comparing UK salaries to US ones is to 1.5x it to dollars. A £150k salary in London is equiv to a ~$200-250k salary in the US. Not bad, I'd say.
While it's of course good by local UK standards, I still think sometimes London needs to recalibrate to pay closer to US norms. Cost of living in London is often just as bad as major US coastal cities. At my work, they recently introduced a London office paying eng roles in similar salary range, and lots of opportunities to move there with help provided for relocation fees. For many the interest evaporates when they see typical dev pay package and CoL in London.
London can be as expensive or cheap as you want it to be. I worked for a startup on 23k when I first started working and my now wife was an undergrad, we still had a studio in Central London (zone 1). On the other hand you can have a town house in Belgravia for prices similar to Atherton.
