A great (and interesting) post from Udayana.
An interesting post, Prof, but seems to me to be quite speculative, without a great understanding of how people, especially Asians, conduct their affairs. Though private education and finance are really off-topic and in danger of revealing too many personal details I could relate some of my own history:
I do not know Sunak or his family and have not looked into their story, but do live a few miles from Southampton; Although I don't normally consider myself as living in a particular community, I could say that my local community is of South Asian origin people who arrived here from Africa - Uganda, Kenya and Tanzania. I am socially engaged with that community and have known many people in it over many years.
I have also put our two children through the private education system ('til university). Note that I am talking about private day schooling, not boarding - which makes a big difference.
ETA: Should also mention that we are discussing financial and educational eras that are completely different wrt. the options possible - preThatcher, Thatcher, Blair, post-Blair.
Practically all Asians who arrived here from Africa during the 60's, no matter how well off they had been there, arrived with no money. Nearly everyone I know from that situation here arrived with barely £5 and no other goods or savings. Some had had good education and some were able to borrow money from relatives still in India. After arrival many worked in everyday normal jobs to retirement, others have built fortunes and earned knighthoods and honours. In all cases they saved what money they were able to and have been self-reliant thoughout their lives. Those that were financially successful (mostly self-employed) sent their children to independent schools, others to state schools - but in all cases they have paid for everything from their own savings - not bought anything on the never-never.
My eldest uncle arrived in the UK, from India, on business just as WWII broke out but was trapped here (after his ship was torpedoed on the return voyage) during the war. He had no money but managed to start and run business such that he was able to send for his two brothers (one of whom was my father) just before the independence of India. Over the next two decades they built a fortune but then, between them, managed to lose it gambling and socialising. This meant that I went through university (after grammar school) penniless, without a grant and the minimum possible support from my mum. After uni I was flat broke .. I found work in an industry that was starting to boom and built up my earnings rapidly to settle into a comfortable, but not outstanding, salary for a professional technical (not managerial) role in IT.
My wife came to the UK with her parents from India in the 60's, they found jobs in the state education system on very modest wages. She has mostly worked on low public sector wages in council services and community roles. When it came time to send our children to school we decided to send them through the private system as we could trust the education provided by local independent schools, where the state schools were in a mess after a decade of Thatcherism. Now, very few of my peers (mostly white English) in my workplace took the same option, they, even the managerial ranks, practically all chose the state system. We managed to afford the fees by budgeting carefully and saving where possible - I can't say we suffered or scrimped to afford them. We got to know many of the parents of other children in the private schools we chose, and very few of them could be considered particularly wealthy - just a sort of normal middle class - doctors, business managers, engineers, academics and self-employed small business people.
My industry peers earned around the same or more than me, I could not not understand what on earth they were spending their money on. In the end I have decided that it was on maximising the sizes of their homes and cars - both requiring huge mortgages or loans. They may leave huge estates when they die - or may not depending on the outstanding loans and taxes.
We had a modest house (never moved in fact) and modest cars. Never had any loans apart from an initial mortgage (at high Thatcher era interest rates)- pretty much the same as all the other Asian origin families around here - even those that have now bought themselves huge mansion like (to me) houses.
To me what is important is how well you are able to use your brain - not how much stuff you have or leave behind when you die.