I don't think it's as uncommon as you might think. I think there are a lot of people who sit somewhere in the middle of the financial spectrum, owning houses worth more than they ever dreamed of and with decent pensions from defined benefit schemes.
I have a friend who has ended up as the only one of her generation. Her parents had siblings but none of them had children and so she's ended up inheriting every few years as her aunts and uncles and her mum's cousins have died off. She also had three godparents all of whom have left her money. None of them were what you'd call wealthy, most were teachers or engineers.
She and I both started off flatsharing in London at around the same time in the early 80s. At that point I earned a bit more than she did. Then she inherited £10k from a grandparent which was enough to enable her to buy a one-bed flat in Notting Hill. Three years later, when I'd scraped together enough to buy a one-bed flat in a dodgy area, she inherited a bit more and traded up to a 2-bedroom house in Mortlake. Subsequent gifts and inheritances, plus stable work and promotions, helped her pay the mortgage off and trade up to a house in Chiswick.
Her parents divorced when she was in her 20s. Both her mother and father remarried, both to partners with some money. Both were in a position to be generous to her and she used to get the maximum tax allowable cash gifts from each of them for Christmas and birthday (currently £3k a year). When her father died he left everything to my friend's stepmother, who died unexpectedly not long afterwards. My friend inherited a large bungalow in the New Forest and around £300k in cash. She grumbled about having to pay inheritance tax for the first time.
My friend is single, was a senior theatre nurse but was able to retire from the NHS and take her pension at 50. She now lives in her own very nice Grade 2 listed house with river view in Twickenham, within a short walk of her mum's home. Her mum gifted her own home to my friend several years ago to avoid inheritance tax. The mother has a full teaching pension of around £30k, plus half her late husband's pension, plus the state pension. Plus whatever she's inherited from her own family and has saved over the years. She pays my friend £20k 'rent' pa for the house and my friend uses that money to maintain the place. In terms of those two properties alone my friend must be worth around £4 million and my guess is that she has another £million+ invested for income, as well as her NHS pension and, down the line, state pension.
Sorry to go into such detail, but I wanted to indicate how someone from a fairly ordinary family of teachers, nurses and engineers can end up being worth millions as a result of the property price boom, buying in the right place at the right time, generous public sector pensions and the good fortune to be the end of the family line. I don't know anyone else from an ordinary family who's benefited quite as much as this friend, but without going through all my contacts I can think of a dozen 'ordinary' people who were able to pay off their mortgages early and retire early as a result of inheritances.