What about the 30 hours of free childcare that everyone, including people on 100K plus salaries are entitled to?
That's not correct.
However, it should be. Childcare funding, education, healthcare etc are universal goods and should be available to all. Restricting the access of those who pay for them (for themselves and everyone else as well) to these things means they will be gradually means-tested with ever lower thresholds until hardly anybody gets them at all. It also reduces "buy in" from the very people that we need to pay for them, so that everyone can access them.
Evidence from abroad shows large buy in from all earnings levels to good state services when they are universally available. I.e. high earners don't resent paying way more than it would cost them to personally access such services (just for their family) in taxes AS LONG AS they also get access to the services and the quality is good. So they will continue to fund it for those who can't, if it is good quality and they get it too. They have paid for it, after all, for themselves and others.
If you go down this bitter route instead and expect these people (who mostly are not rich or wealthy, just earn more than average but also usually have higher expenses too in order to do so because they live in expenses places in order to do so, and who work long hours and make huge sacrifices of time with their own families in order to do so) to pay for what you want, but tell them they should pay for it for you but not be able to use the service they are funding themselves, then you lose that buy-in to the welfare state and, indeed, to the very idea of society.
The result is that means tests are put in place, like with child benefit as an example, because many people considered £50k a good salary, not understanding that this doesn't go far at all in many areas. So now these people are funding this, yet don't get it themselves. Then with fiscal drag, you end up with more and more people not eligible.
To be cynical, if I was trying to design a way to remove any support for the welfare state, introducing means testing is the obvious way to go about it. Then you gradually lower the thresholds (through fiscal drag this won't take too long because of compounding, even in lower inflationary times) and before long you end up with one group of people funding things for another group of people and getting nothing back. Then you have a very easy way to convince them to scrap it entirely, because why should they?
If you want a welfare state that is sustainable, people who can contribute need to have the decency and respect for everyone else to do so. But you also do not want means testing for basic things like childcare funding. Because by doing so you will undermine the public support for it and ultimately bring about it being cancelled altogether.
This is why any attempt to means-test the state pension will be the death knell of the whole thing. People simply won't be prepared to be the ones who pay most in their lives and get nothing back at all. For now, higher earners pay far more than they get back, but will accept this. If a Government then says they'll get nothing, what will happen? Whatever threshold that people think is "fair" at the time will gradually lower through fiscal drag or other measures and eventually nobody (or very few) will get anything at all. Pressure to keep the amount up with inflation will vanish, in fact the opposite will be the case.
This is the stuff people don't think about. Blinded by bitterness or jealousy, they do not grasp the long-term impacts of these decisions and that ultimately raging against people who pay for the services for everyone accessing those same services themselves might seem like a nice idea now but, much like with the Brexit insanity, it seems people with such mentalities do not have the foresight or wider thinking to grasp the big picture and how this will impact them as well in the long-term. It is such an easy way to get people to vote for their own demise, by manipulating them into bitterness against others who they perceive to have more than them, even when these are the people providing for them!
If you want to carry on this way then fine, but it won't end well. The types of countries people here SAY they want to emulate involve universal services for everyone, and also middle and lower earners paying FAR more tax than they do. Not expecting everything to be paid by other people. You will never create a proper society that way.