My family were farmers that diversified into property and I've done 3 self build houses myself now. We still have around 80 acres and the best use it has is for borrowing money against, unless I can get a wind turbine on it.
Farming it properly would give very little income and be a huge time sink.
Land prices are around 10k per acre now and I've seen some pony paddocks go for 16k.
How much land are you thinking about, as in enough that you'll have to buy machinery or enough that you'll scrat around by hand?
You can build a certain size farm building without planning permission.
Forget about getting a piece of land and getting a house planning permision on it, everyone is after the same thing and has been for 20 years, so the all easy bits have gone.
The council won't let you live in a temporary structure that doesn't have services and then if you add services it isn't really a temporary structure and so will need full planning.
There is a loophole where you can get an agricultural residence through owning some land but then renting a large ammount, then once you get planning give up the rented land, but councils are becoming wise to this now.
If you want your kids to grow up in the country I'd suggest buying a house with a padock that you can potter about with growing veg and couple of pigs, etc and all you'll need is a little old tractor and a few bits and bobs that will cost you about 6k and keep the farming to a hobby, as the reality of what your looking for is not like river cottage.
