I am American, but did spend 3 years in London as hire #1, later becoming CTO. This was SV company that moved headquarters to London, this was slighty larger scale than you're indicating, but same order of magnitude when I moved to London (2011-2014).

The first thing I'll say is, advice about negotiating hard—thinking through BATNA and all that—is not wrong, but it's also a specifically American perspective that you don't want to deploy blindly. Doesn't matter what culture you are in, personal relationships matter, so be thoughtful.

That said, you also don't want to be taken advantage of. It seems implied one of the co-founders is technical, but you're leading most of the code/infra level technical work, and you aren't easily replaced. It's hard to know just from this how strong your position is though. Are you the strongest engineer technically? Are you an ideal fit to lead the next phase of growth? If the answer is yes to both, then $75k + 0.2% equity feels light.

I never had EMIs, but I understand they are more or less equivalent to ISOs. A legit engineer #1 that serves as a tech lead should get 1-2% as a rule of thumb. In this case though, you say you started as junior, so 0.2% may have made sense, but you've grown and are contributing a lot more. Equity should not be a one-time thing, especially as you step into larger roles.

You're right folks advise against sacrificing cash salary for equity in private companies, because a huge percentage will go to zero. Yes, it's a lottery, but in this case you're already working for this company, and the trajectory already sounds better than 90% of startups (although "almost profitable" could be spin), so equity gives you upside. Note it's also easier for them to give you more equity because it doesn't require precious cash, and the sooner they give the equity the more valuable it will potentially have (lower strike price).

Also, I definitely agree with folks saying that your personal living situation should not factor into negotiations explicitly. What matters is your worth to them, not your expenses. That said, if you are comfortable that you can take more equity, and you believe in the trajectory of the company (and the financial acumen of the founders), and you can afford to take the risk, equity is what mints millionaires and create a real sense of cohesion in the core team. On the other hand, if you don't feel solid about the company's future and don't feel embraced by the inner circle, then just ask for as much cash as you can.