> London is notorious for low SWEng salaries
I was actually going to challenge this before I did a bit of research and discovered you're right - the average wage for a software engineer is £47,500 (https://www.cwjobs.co.uk/salary-checker/average-it-salary). That's ugly.
I'm from Liverpool originally (live abroad now) and I have friends in Manchester earning £50-60k... in the North of England. That's a big wage in that area.