Really? I am utterly surprised by the thought of anyone choosing finance over academia for fear of "letting down the family". I grew up thinking of "Wall Street" as an uncultured and not very respectable profession.
My dad was disgusted when I told him (2003, during my junior year in college) that I was considering Wall Street as a profession. My parents both wanted me to get a PhD, and strongly insinuated that finance would be a waste of my talent.
I come from a family of inventors, architects, and writers, so although I grew up solidly middle-class, and my parents would've been happy with my choice had I been a high school teacher, the thought of me working on Wall Street was seen as a massive "step down" into unpreftigious nouveau-riche territory. (I softened my view toward Wall Street upon moving to New York; a lot of quants are brilliant, educated, and cultured people. I still do look down, reflexively, upon any "profession" connected to real estate. I can honestly say I'd never marry a woman who worked in RE, and only a woman from a real estate family if she had been purified through an elite college, a filter I otherwise don't care about in the slightest.)
I'm surprised that upper-middle-class UK families don't have an even stronger blue-blooded prejudice against "working on the exchange". Growing up, I always understood being an intellectual (academics at the pinnacle) as the epitome of preftige, and investment banking as the thing you did when your family lost its money/standing and you needed to buy it back by sacrificing ten years of your life to something unpreftigious but lucrative.