If you can change your caste, then it can't be a caste system, can it?
You can't be born into it, and the system has traditionally honoured thousands of 'normal' people that have been nominated, usually by their peers, for doing work in their field or community.
https://www.gov.uk/honours-committees
As you can see, some of them are themselves honours recipients, and some are not.
In no sense is this a self-awarding organisation - and the only reason there are so many recipients on the committee is because honours are given out to just about everybody who has achieved anything of note.