You got some answers that essentially inform you that CEOs that have £200k written on their paysheet may in fact get much more. I'll take the opposite point of view and talk about people who (according to whatever definition) have a £200k/year income.
How can they afford it
Guess no 1: not all of them can (in the sense that it is quite possible to end up with negative net worth at £200k/year income - particularly if you immediately want to show off with brand new luxury cars, luxury holidays and a large house in a very representative region).
Guess no 2: not all of the £200k/year CEOs are equally visible. There is a trade-off between going for wealth, large house, and luxury car. I deliberately ordered the three points according to increased display of "wealth". However, display of wealth usually comes at a cost (in a very monetary sense). And there are ways to get much display without having much wealth (see below: lease the car, also the mortgage on the house usually isn't displayed on the outside).
You also need to take into account how long they are already building up wealth. I guess the typical CEO with £200k/year you're asking about did not just finish school and enter his work life in this position. It would be very interesting to see how income, accumulating wealth (and possibly "displayed wealth") correlate. My guess is that the correlation between income and accumulated wealth isn't that high, and the correlation between displayed and actual wealth is probably even lower.
they possess luxury cars, large house and huge savings
Are you sure these are the same managers? E.g. the ones with the huge savings are and the ones with the luxury cars?
I'm asking particularly about the luxury cars, because such cars loose value very quickly and/or are often not owned by the driver but rather by the bank or leasing company. Which on the other hand offers the more savings-oriented CEO who is not that much interested in having a brand new luxury car the possibility to go for a one-year-old and save the rest. Knowing that, your CEO should be able to buy a one-year-old Mercedes SL 350 / year. Or a new one every 1 1/2 years (without building up savings or buying a house). However, building up wealth will be much faster with the CEO going for the one-year-old as the brand-new car option amounts to loosing ca. £20 - 30k within a year.
An even-more-savings-oriented CEO who keeps his existing Mercedes 300 TD for another few years, thinking that this conservative choice of car will be trust-inspiring to the customers. Or goes for the SLK thinking that most people anyways don't know that the K between SL and SLK halves the price...
However, if you just want to be seen with the car: after an initial payment of say £8-10k, you can get a decent SLK 350 (not the base model, either) at a monthly rate of ca. 600£/month or less than £7k/year. Note however, that this money does not count towards any kind of wealth, it's just renting a nice car.
In other words: If driving the SLK 350 is your absolute goal, you could in theory have that with a net salary of £25k/year (according to your tax calculation, that should be somewhere around £35k / year gross), if you have the savings for the initial payment (being able to make the initial payment may also help convincin the leasing company that you're serious about it and able to pay your rates).
There are also huge differences in value between large houses, compare e.g. these 2:
And, last but not least, there is a decided one-way component in the timing of priorities here: it is much easier to go and get a luxury car when you have savings than first going for the luxury car and then trying to make up with the savings...
I forgot to answer the question in the caption of your question:
How do I build wealth
By going on to live as if your income were only £50k (as far as that is compatible with your job) - I gather the median gross income in the UK is about £30k, so aiming at £50k leaves you a very comfortable budget for luxury spending. If you want to build up wealth faster, adjust that.
In general, if you can manage to withhold much of any income increase from spending, that will help (trivial but powerful truth).
From the leasing calculation you can conclude that you basically have no chance to show off your wealth by luxury cars. That is, you'd need to go for luxury cars that are completely incompatible with with building if you want to show your built up wealth by the car: there are too many people who even destroy their existing wealth in order to display luxury.
At least if anyone is around who has either a correct idea what luxury cars cost (or don't cost) or will look that up in the internet. Also, people who know such things may also have the idea that the probability that such a car was downright paid (wealth) is small compared to the probability of meeting a leased or (mortgaged) car. Which means, the plan to show off doesn't work out that well with the people you'd want to impress. As for the other people: just a bit of display you can get far cheaper:
If you really want to drive the SLK, rent it for an occasion (weekend) rather than for years.
I met a sales manager who told me which rental cars they get when important customers from far east are visiting. The rest of the year they drive normal business cars. You may want to choose a rental company that doesn't write their name on the license plate.
Apply the same ideas to the decision of buying a house. Think about what you want for yourself, and then look where you can get how much of that for how much money.
Oh, and by the way: if I understand correctly, the average UK CEO wage is £120k, not £200k.