I am going to be brutally honest, with the risk of offending someone/possibly more than one person.
Both my sister in law and I wanted to move to the country, and only one of us did. I moved when my dc were young to an idyllic spot - think picture postcard village with beautiful rolling countryside and friendly locals. My sister in law stayed in London. So we can and do compare the two:
The upshot of coastal/country relocation:
Advantages:
- Depending on the age of your dc, if they are young enough they will have the most lovely childhood, building dens, climbing trees, nature based fun like riding and freedom, beach days and swimming in the sea - sailing etc. They will stay 'younger' for longer, and there is no hot housing going on here at all.
*It is peaceful and safe, nothing bad ever happens here. It will make the village news if a cat goes missing for a day or two.
*It is civilised, school behaviour here is very good on the whole, grades are very good.
*It is very relaxed, most people are relaxed. There is very little/no stress.
*There is very little access here to drugs and zero drugs culture here. Teens tend to be quite wholesome, they hang out at each others houses, have parties in the garden in the summer. It is low key.
*They go to London for the odd weekend for shopping etc maybe six times a year, but are not there all of the time.
Disadvantages:
*There is less to do for teens in coastal and country areas, this helps keep them out of trouble because they need lifts everywhere in our case, and they have good solid local friends they see a lot. We don't mind driving them, but it won't be for everyone.
*Independence is harder until they can drive at seventeen, they will be relying on you
*Street wise - my nieces are far more streetwise and very focused on trends etc, they are 'fashionable' where as my dc tend to wear what they want and don't care so much. I think it is cultural
*They found it easy to get work experience and jobs in London.
In making your decision, you have to imagine that whilst the children are younger there are HUGE upsides, but as they get older it may be less obvious. So if your dc are young, I would say go for it now. If they are just about to hit the teens - I would move to the outskirts of London, Westerham, Sevenoaks etc or Ascot and surrounding areas and stay closer to London.
My nieces have done very well and all getting good jobs, are able to stay at home and have lots of work opportunities. I guess your dc can always move to London if they wish once older. My dc are not quite at that age yet, but are very fit, healthy country loving and are not quite so 'edgy' as they don't have to be.
I would move in a heartbeat, it was the best thing we ever did leaving the rat race. I would strongly urge you to rent for six months or longer (if you can do so over the summer and 'try out' your new life before you buy if you can, and see what the reality is like before you commit. Many London families move here, and some of the parents find it just too quiet for them.
It was by far the best decision we ever made. Dh commutes into London daily or used to.
Oxfordshire villages etc are within reach of London for example.
You DO only have one life, but you need to make an income, so if you are looking at Devon etc be sure there are sound jobs there for you before you go.