From my perspective, I moved from Glasgow (very similar to London in that there is so much going on, very multicultural and I had loads of friends) with my dc to Dorset.
The first year was hard, really hard. And I grew up here! But honestly, I don't regret the move at all. We have been here five years now and my girls are now 18 and 11. Oldest has gone off to uni but they have spent the last five years on the beach, kayaking, swimming, sailing and generally being outside all the time.
My oldest in particular, who was 13 when we moved and not happy about it, really has grown so much. She knuckled down at school and has made friends really quickly. Looking at what her peers are doing back where we lived, I am so glad we moved. None of her old friends are at uni, most are working dead end jobs and I am glad that she has seen there is more to life than hair, make up and going out. Yes, she does these things but she has been involved in so much here that opened her eyes to a wider world.
I sometimes miss city living. Yes, public transport was awesome but I have a car here and my youngest walks to school. We live in a village just outside a main town (10 mins drive). Schools are brilliant and youngest has made loads of friends too.
It's a healthier lifestyle for us all. There just seems to be more of an outside living culture here and most families are out doing something like sailing, cycling etc together at the weekends.
I have made a few friends and I'm quite happy being involved with the dc school and helping out with things which lets me meet more people.
Don't say never. Why not book a holiday down here and come and see for yourself what's available.
It's not the arse end of nowhere here, there is lots going on and yes, you may need to drive more but there is a whole new world available to your family.