I spent my childhood in zone 6 and my 20s and early 30s in Zone 3 until I moved West with my husband when my DD was born. I continued to work in London, but subsequently we moved further West and I hated spending 3 hours a day commuting so I found a job nearer to home.
I'm now mid 40s with 2 kids, happily living in a large 6 bed house with a big garden and a double garage and plenty of off-street parking, which is worth about £700k. We are catchment for an outstanding Primary and Secondary both an easy walk or bike ride through green pathways from home. We are a 10 min drive or 5 minute bike ride from our town centre. I simply can't imagine I could find a similarly lovely 6 bedroom house in a similarly lovely part of London for 700k.
The regrets are, it isn't as diverse as London, so it can feel a bit provincial. If you love the theatre or fashion or live music or museum exhibitions, then you can't really beat London. I'm pretty excited that the Elizabeth Line will put the centre of London within easy reach (albeit no doubt at a shocking price).
I also do slightly regret moving away from a vast host of job opportunities in London, but my career has taken second place since I had kids anyway. Was this the best choice? So far I think so, but when I'm 50 or 60 I may regret it.
My DP and I both decided, longer term, that the biggest downside was commuting to London daily. I do know couples nearby who both commute to central London, it's definitely easier with older kids who can get to and from school alone. Still, not fun if both parents arent home until 6.30pm every weekday if your kid(s) have got home at 3.45pm.
I cannot see myself wanting to work in London again. When you have adjusted to getting home from work within 20 minutes, a long commute seems like insanity.
To state the obvious "Outside London" is a very large area. I do not live in Kent,.Hampshire or Surrey, so perhaps my experience is significantly different. I would definitely NOT make the move if I couldnt find a much cheaper property near excellent state schools, versus what's on offer in London. The property cost savings of moving out are absolutely key, either because you will pay a lot more to commute OR because you will drop salary to work outside London. Obviously you cannot trade up to a much larger house and garden without paying a price to live near good schools and a town centre/station. But assuming you are not comparing apples with pears, it doesn't make sense to pay the same amount to live in the outer commuter belt. Low crime, green space, low pollution isn't worth that much.