I'm a senior software engineer and am earning £70k in Edinburgh. You may be getting underpaid depending on where you are.
I have many friends with the same years of experience as myself, and similar tech stacks. They're working for smaller organisations across the south of England and on roughly £28-30k with few/no perks past the standard UK pension payments.
I think a lot of people are underpaid in the UK (including the parent poster), in particular those at smaller companies and smaller consulting agencies. However I imagine it's less of an issue in London.
On QoL, I have a 2 bedroom flat in a nice area within a 15 min walk of tech employers. This is equivalent to owning prime real-estate in San Fransisco.