Good for you, i work in finance in london and don't quite make that much, none of my friends in other places like JP, Goldman Sachs, Amazon, Instagram ecc does make 200k pounds/year base, maybe in tc yes. Skill issue probably.
I would say 90-120k pounds/year base for a mid-senior engineer in FAANG/Finance is what most of us is being offered right now in London, based on my recent experience. What i feel is that many of us are being heavily undercut right now, me included, while consultancy keeps it's pace and everywhere outside London it's a bloodbath.
There is no Atlassian salary data for the UK on levels.fyi. I think you are just quoting American salaries.
Deliveroo L6 is 135k average, but I think it is more realistic to look at L5, which is just around 105k.
Also, 600 a day as a contractor is nowhere near 150K+, it is 132K paid to your company's account (assuming 220 working days a year - but that's not a salary!), or you go via an umbrella and then it is even less. A 600 daily rate is pretty average in London, but only if you work for a bank - which classifies as "finance", I guess... But then you are not an employee, you are a contractor, which is very different.
On levels.fyi there is one Atlassian P60 engineer (senior? staff?) in London making 230K+.
On L60-L50, I’m not saying that everybody makes 150K+; I’m saying that it’s not impossible for a good senior engineer (or staff or principal, as we call them nowadays) to make more than 150K at a non-FAANG company.
Maybe I got my maths wrong with contractors. I never did it myself, but I know they do crazy things with taxes (eg hiring their wife, son, dog and plants, to reduce the tax bill) and that they don’t take holidays. So I multiplied 600 by 5 and then by 50, got 150K and I assumed they’d make more than an employee earning the same.
I'd left the city 5 years ago, just before IR35 hit, so my info is not quite up to date, but in general I would say that nobody can work without taking any vacations - both for health and legal reasons. Some contracts may even stipulate a maximum number of days you can work in a year (that's where my 220 number is from).
And it used to be that you could do some tricks to lower your taxes, but there is a limit, and after the IR35 reforms many firms decided they don't want contractors, or they are pushing you inside IR35, which means PAYE taxes, and worse (because you still have to do the accounting for your company, pay corporation tax etc). So contractors are earning LESS than an employee with an equivalent salary, plus there are some extra burdens. It used to be that a regular engineer (without any management responsibilities) could achieve higher income in the short term being a contractor, but I'm not sure that is the case anymore.
Outside London, if you can find a place willing to take you on as a contractor it may still be worth it, because your daily rate will be less, meaning you may not reach higher tax brackets, and compared to almost everyone else around you you would still be king.
Apart for consultants which is what I recommend people get into for a high paying job, even looking at levels.fyi, the average pay is actually lower in the UK.
Take Samsara, on average basis an entry level engineer in the US pays higher than a semi-senior SWE (SWE II) in the UK, taking into account the base as well for a senior also looks dismal for UK engineers.
Even when these companies are public, UK salaries just don't seem to be competitive or appealing and this all just proves my point. Just go to the US, FAANG, finance or just be a consultant.