If you're doing $70/hr in the UK at CISO level you're way under some of your competitors.
Heck Pentesters charge more than that and they're 50%+ cheaper in the UK than the US.
My hourly rate in the UK as an Big-4 Infosec consultant 15+ years ago was way more than that and I wasn't doing CISO work. Partners (who were the kind of people doing that kind of work) were 10x your rate back then.
It's actually a similar price in Germany. There are higher paying jobs in Berlin, but in general it's not unusual to have this price in Europe. France and Spain is even lower.
There are definitely companies in the UK that will pay competitive rates for tech. $70/hr is lower than the median contracting rates for the UK, and I'd be suspicious if someone with 20 years experience was that cheap. I'd expect at minimum to be paying 1000 GBP/day.
I had 15 years of experience when I last updated my rates - and I chronically undervalue myself. I’m responsible for the better part of a billion pounds of revenue, without exaggeration, across my clients, over the decades.
Part of the issue I’ve faced is that I usually start working with folks when they’re 2-3 people, and I grow them - but my rates end up stuck at the 2-3 people company level, not at the 1000+ person company level that they’ve mostly become.
I also consistently manage to get gipped out of equity, as I’m always “just madaxe”, who humbly grinds away and doesn’t feel right taking a slice of someone else’s pie.
"and doesn’t feel right taking a slice of someone else’s pie"
I hate to say it, but you need to get over that. This very mindset has screwed me over more times than I care to think about. I'm in the $2B+ generated revenue part of my career. I've got a lot of scars, bruises and broken dreams that brought me here. Built an entire start-up, that sold for $256M, got screwed out of $2M. That was on the low-end of what I've lost in various endeavours. And I have stupidly made that mistake several times. Over the years I've learned some hard lessons.
I now take the approach that "I charge this much per day/week for my time, if you cannot afford that and wish to give me equity in lieu of (some of) my pay, these are my terms." And I don't do 4 year vesting with 1 year cliff. If I am taking a significant pay cut, e.g. 60% to 70% from my usual day rate, the cliff is 90 days on an accelerated vesting schedule. And it is a grant, not options, I'm not giving back money to get what I earned.
You also need to start negotiating your contracts to have a quaterly or bi-annual rate increase from "I'm doing you a solid here with a big discount" so that three years later, after built all the tech for the start-up, you aren't earning less than the Junior who struggles to remember the difference between margins and offsets. On client discounts (I've stopped giving them except where large chunks of equity are concerned), you can backload them too, so that should the client cut you loose because you bumped your rate by 10% last year, as stated in your contract, they pay a termination fee. Some clients will balk and nope out, those clients you don't want. It took me decades to figure out I was allowed to say "no" to potential work.
Right now I am charging less than what I have in the past, $1,000/day as opposed to $1,600 to $2,000/day, because I need some stress free time, and at 6pm, I turn off my computer and forget about my work.
Have you considered finding somebody to act as your “talent agent“? I don’t know exactly how this would work, but with so much money being left on the table I think it makes a ton of sense to be creative. I totally understand how awkward it can be to ask for more, but if part of the block is your own personality, there must be someone out there who would have less of a problem asking for what you deserve. The ROI would almost certainly be huge regardless of their cut.
It’s just that in the U.K., technology skills have little to no value.