£150k is ~$196k base. I don't really see how that's much much less? My friend is an L6 at 220k base (with a shitload of equity). Definitely within the range.
Workers in UK also work less than their US counterparts (paid holidays, parental leave, sick days ...) [1]. Would make more sense to compare these countries by hourly income, not yearly.
My (current) experience is that the London teams at my FAANG work no less than the US ones, and indeed often much later into the evenings to accommodate meetings. And everyone works fewer hours than those in finance.
Base is not that important especially at L6. How much stock is your friend getting?