I had a conversation with my sister not so long ago about this. Between her and her partner, they earn in excess of £85K a year. House prices are soaring where they live, but they're a financially sensible couple who have paid off their student debts, saved up while renting in London, got together a decent house deposit and eventually bought a modest 3 bed semi detached about 50 minutes by train outside the city. They don't indulge in any luxuries (no sky package, no fancy day trips, no expensive spa days, etc) or book extravagant holidays - they had a cheap caravan holiday to Cornwall in September. Their mortgage is naturally quite high, but still 'affordable' on their salaries. They run one car (bought second hand with savings) and have the same bills as everybody else. My sister's partner commutes to London 5 days a week and they will soon have to pay £1200 on childcare every month.
Having done the sums in my head countless times, I genuinely don't know how they're managing 
And awful as this is, I think I, as a single parent who works part time and lives in Scotland, actually have more 'disposable income' than they do. Because even though I earn a piddly amount, I still have a couple of hundred to play with after the rent and bills are all paid. And I can't see how they have anything left 
I can absolutely see how the middle class is being squeezed left, right and center. Because when you're having to pay London/M4 corridor rates, there is nothing left once the high mortgage, bills and extortionate childcare fees are paid. And there is no financial help available for them. The truth of the matter is, £100K can be the difference between affluence and just getting by when you play the postcode lottery. Where I live, that kind of monthly income would have you living like kings and queens. For my sister though, it's a very tight squeeze.