WE moved last year to a semi rural village near small town a few miles from a city. We specifically chose somewhere with good transport links (on train line) as wanted to avoid becoming reliant on car and wanted access to city life if we felt the need.
Main up sides:
Beautiful countryside and closeness to nature, cold frosty mornings, peaceful sunny evenings, birdsong - I feel completely alive after all those grey years in London.
Streets are much safer and so DCs have much more freedom to play out, go to local shops on own & when older will be able to get bus/ train into the nearby city for culture/ shopping etc. Nearby city is university city with lots going on.
People are less stressed, less agressive and have more time to pass the time of day.
Schools are good and, according to DCs, behaviour a lot better in class so more time spent on productive learning (not sure to what extent that is a London thing but probably reflects relative levels of wealth)
After a few false starts have found like minded friends. Some people are dull & narrow minded but its such a great location that I always held out the hope that "people like us" would have spotted this too and moved here, just needed to find them.
Down sides
Public transport is very expensive, especially buses. We have ended up driving a lot although we do cycle as much as poss. HOwever I would feel much happier about letting DCs out on roads on bikes on own when a bit older as drivers are much more cautious about cyclists than in London.
JObs are worse paid and less choice unless you happen to work in one of the local industries. In my field there are about two jobs a year compared to about 30 that I could have applied for in London.
Cultural events are rarer and especially free ones - have to pay for almost everything. However there is loads of sport and lots of people willing to give up their time to run sports stuff for kids.
Not necessarily cheaper - council tax, water rates and heating bills (we are now on oil) all more expensive but insurance a lot cheaper so has kind of evened out. Houses a bit cheaper too. However we are saving a lot on things like holidays and meals out as we no longer need these to "escape" from London.
Less multi cultural which can occasionally lead to narrow mindedness and subtly racist attitudes stemming from ignorance/ fear of unknown.
Think you do need to pick your place and get all your key things in place before you leap - we had to wait for DP to find job. Did consider commuterland but so glad we didn't go for that - DP & I now travel only half hour each to work on blissfully empty trains.