Maybe you missed a two, as you'd have £2,200 in your pocket.
As for the stealth tax, that is what you call "employer contributions"
At 100k salary, those are 13k ish, thus, you dont earn 100k, you earn 113k
Just an interesting addition, i know people earning 25k, who refuse overtime with the argument of "i'll just pay more tax".
So in terms of my decision to accept a 6k raise from 100k, the answer might be yes or no, if the answer is a no, and you change that marginal rate from 62% i believe, to zero, meaning i will get the full 6k extra after taxes. My answer will still be no.