@PurpleTitan Your are right when you say I think the UK system is more of a meritocracy. Split the admission decisions into academics and finances if you will.
There is no way you are getting into top schools without superb academics no matter where you went to high school. It is true that independent school kids have more resources and are coached from a young age for entry into places like Oxbridge, but you cant blame the kid for choices the parents make about their education, or from being from wealthy background. A kid from a more disadvantaged background does have a chance for entry even if his/her academics are excellent but not stellar, there is the interview stage which is designed to pick out such candidates. That works both ways, it will weed out those independent school kids who are coached rather than who have true intellectual curiosity. Perhaps the biggest advantage for independent school kids is that UK kids are given conditional university offers, so if you come from Westminster who send dozens of kids to Oxbridge each year and whose links go back centuries, its not a stretch to believe a known commodity as the Westminster kid will get the edge over a kid whose high school has never sent a kid to Oxbridge.
In terms of finances, tuition is set for every school, 9000 sterling per year no matter where you go. If you cant fund yourself then you can take a government loan from the Student Loan Company. This is not a loan as it is in the US, you only pay it back if you earn above a certain salary and if you still have student debt after 30 years it is written off. It is not an ideal situation and will blow up in 15 years or so, but the fact is finances should not preclude any kid from going to any university he/she can get in.
Admissions in the US, call it what you will, social engineering, affirmative action, holistic admissions… its is designed so the college can admit whomever they choose for whatever reason they choose, and as we all know not necessarily based on academic achievement or potential.