If you have chickens, there are several considerations. What is best depends on your situation.
If you have plenty of land and live on a dirt road, free range is great. But, chickens wander, so this requires space and little traffic, and neighbors who are understanding.
A run is great, but if it's too small it'll stink and encourage disease.
For a small chicken lot, you'll need to do a little work. Pour a concrete platform (it doesn't have to be perfect or beautiful) at one end of the pen area. It should be four foot deep and one foot wide per chicken, plus another three foot for a roost shed(for up to six chickens).
On this concrete, you'll be putting nesters and a roost shed. One nester per chicken, one foot wide, two feet long and a foot or two high is fine. Make sure to put a board across the bottom to keep the nest material and eggs IN. You can use shipping crates turned on their side for nesters, but make sure the nester has a solid roof to keep out rain.
In each nester, put a nice bed of mulch. Mulch makes it easier to find the eggs, it stays cleaner and nicer smelling than straw, and it's easy to clean out. Cedar mulch even keeps out bugs.
Put in a nice shed with some perches (An old ladder works great for perching, so a shed with a ladder leaning on a wall really works great).
The yard itself can either be free range, or it can be fenced. If it's fenced, then you should figure on using more space than recommended, because chickens can stink, and they fight if they feel confined. I'd recommend ten square feet per chicken, and make sure it's an eight foot fence to keep any from hopping over (some can fly a bit).
Chickens can be bought from hatcheries, farm markets, or you can go to a local farm that says "Eggs for sale" and ask if they'd be willing to sell a chicken or two and if not, where did they get theirs.
And, keeping chickens doesn't require a license so long as you aren't within city limits, at least in the U.S.. I don't know for sure about the UK.