As someone who has spent 10+ years in boarding public schools, I feel I ought to comment on some of the misconceptions here.
Firstly, why is the "two-tier" system such a "disgrace"? Sure, many believe that good education is a basic human right, but so is food, or even shelter. Saying that the concept of private education is a disgrace is quite ridiculous. If money shouldn't be used to buy a better education, then should money be used to buy better food or housing? It's a ridiculous statement that appears to be fuelled only by bitterness. Taxes simply do not provide enough money to bring every state school up to the standard of the top private schools in terms of facilities and staff, and so expecting state schools to be of such a standard is rather silly.
Secondly, you seem to be basing the quality of a school on academic results alone - but this again is ridiculous, as that is not the only measure of a good education. A good education should have breadth as well as depth. Did your state schools offer all the extra curriculars that a good public school would offer? I doubt it, simply because the facilities cost a lot of money. Were you given opportunities to go on school trips abroad several times a term to learn about different cultures or gain real world experience? Again, I doubt it.
As for the whole "success" argument - only you can alter your future and make it a success or a failure. The education is just a push in the right (or wrong) direction. Going to a private school will often give you more opportunities and allow your skills to flourish and thus ease you into a more successful career than you would otherwise have had, but ultimately it's up to you and not your school. With the increasingly meritocratic workplace the old boys' tie doesn't have as much of an impact as it used to be, but the old boys' network is still very much alive and, whilst I don't like to say it, that is probably one of the biggest advantages of private education.