You’re quite right about the age profile, sp. Older people who knew these areas many years ago have seen the rapid change foisted upon them and they don’t like it. Younger people know no different and just accept things the way they are. Eventually, of course, there will be nobody left who remembers “the good old days” and the transformation will be complete.
The majority of “local” shops in most areas of London, Zeuhl, are owned by the local council. Fred has hit the nail on the head here. Rent and Business Rates on these premises are astronomical. A barber in a local parade of shops that I know had his rent “reassessed” by the Council almost two years ago. The process got off to a bad start with the council wallah only being prepared to visit on the day the shop remained closed (“that’s the day I visit that area”). When he finally did visit he measured up the premises (which had not changed in dimensions since the shop was built) and calculated the rent and rates to be £31,000 pa - an increase of some 28%. You have to do a lot of £8 haircuts to take £600 in a week (before you make any money for luxuries such as water rates, heating and lighting) so my mate the barber closed his shop, as it remains today. No negotiation was possible with the council and they obviously prefer to see empty shops rather than some in use at a reduced rent.
Of course this does not explain “white flight” but may go towards explaining why so many “local” shops lie empty.