Anything close to £100k for a hands-on employee position was almost unheard of in the UK a decade ago, even adjusting for inflation. You might have found that much working in a particularly well paid field, which mostly meant finance in those days, for a big firm in London. For most of the industry the salary probably capped out at around £60k in today's money or maybe a bit more in London, but you could hit that ceiling and get a senior title in maybe five years if you were OK at your job. If you were lucky you might also have landed a nice bonus from a profit-sharing scheme or some stock options that came good.

A formal technical career path stretching well beyond senior level, six-digit developer salaries and the kind of additional compensation in bonuses and stock that we see today are all much more recent shifts in the market. We seem to be tracking a few years behind similar developments in the US as the big money and demand for more capable developers find their way over here.

You can definitely still make more going independent than most will as an employee if you have the ability and inclination but the market has been seriously distorted by the IR35 changes recently (or more accurately, by many clients who don't understand those changes and reacted negatively at the same time) so beware of that if you are thinking of a big career shift.

Everyone I know in the UK who made Serious Money(TM) by developing software made it from an exit when they were a founder or early employee.