Following.
We moved away from London almost two years ago, just before having our first child. Leaving London had always been a long term plan. That said, I desperately miss our friends and wider social network. We've found that it's very very difficult to make new friends when you have a toddler and don't get out much full stop. We hope to try for another soon so will (hopefully!) have even less time over the next couple of years...!
I know there are loads of advantages to living in a smaller, but still vibrant, city and try to remind myself of these. But it seems paradoxical and ironic to me e.g. that we now have a house (rather than a flat) with the kitchen diner I longed for but no friends to invite round for dinner. We now also live much closer to amazing countryside and to opportunities to take part in sports and activities we love but now don't have the time to participate in them.
DH has struggled to make friends especially, due to his work being far from sociable, having less time to devote to old hobbies and sports and not having a ready-made network of acquaintances in the same way that I do with other mums. (Isn't it weird how so often mums form reasonable or even very good friendships through having children but dads do much less so?)
I've already said to DH that if we don't feel more settled in a couple more years then I would seriously consider moving back to London / the South East. Might seem a crazy move just as schools start to matter (schools here are generally good) and especially as we'd be limited on where we could afford to live and would probably have to look at less desirable or less convenient areas that we had considered before making the big move out of London but ruled out back then.
If not then, then maybe when our children leave school. I can't help thinking that our children will inevitably end up in London at some point, whether for study or work, and that would also draw me back, to be closer to them and to be closer to enjoy what London has to offer when our children are independent.
Moving back in the next few years would be financially challenging as London property prices seem to have rocketed in the time since we sold up and moved.
We do have friends come to visit and also go back to London to visit others (I always get pangs when we do!). But I regret not being closer to good friends (and some family) in that area while our child(ren) are young to share in the special early years together.
Sorry to hijack! Interested in others' responses and what the OP decides.