That's not a common compensation at all. I think USA gives way more choices, at the very least finance, big tech and start-ups (that actually offer noticeable equity, unlike UK).
Outside London it varies a lot though... I'm from the South West and £50k would be a good salary there. But that's no different from some places in the US. If you live in a small town, of course there is less opportunity.
But most people who know their worth become contractors. I've had to work with people on £500/day who I wouldn't even trust to run the tests properly. Selling yourself as a "senior <insert hot language of the day> developer" you can easily command a few hundred more. And then there's fintech which goes even higher.
In the UK there isn't that much difference in security from being an employee vs a contractor (you still have state health insurance at the end of the day). Even without the higher rates, the tax benefits alone make it very beneficial, which is why IR35 regulations have been brought in. I know someone who has a company car (Porsche Taycan) which they use to drive to the company yatch...
For anyone watching, £100k ($136k) pre tax is £67k ($91k) post income related taxes.
That's about the same tax rate as someone in California according to https://us.icalculator.info/tax-calculator/annual.html