Where's the best places to buy hens for laying?
Find a reputable breeder near you - what sort of area are you in? (north/south/east etc)
What type of feed would you suggest?
Either layers mash or layers pellets. Layers mash is more interesting for them to eat, and can help prevent some types of boredom behaviour, like feather pulling but layers pellets are tidier.
Best types of coops etc?
You can either get a plastic eglu type thing or a traditional wooden one. If you have foxes then they probably need some sort of enclosed run.
Average cost of keep per month?
The main costs are the setting up costs - cost of wood mainly. After that they're very cheap - just the cost of the food really.
Expected laying abilities?
Depends on the breed. A modern hybrid will lay about 320 eggs in their first year.
What to do if you then want to breed? (I.e: Do you then buy a cock or can you take one of your hen's to a breeder and use theirs?)
You could get your own cock, or you could buy fertilised eggs if you want a specific breed.
Is there anything else that I've left out that I'd need? (do you keep them in a different type of coop during the winter etc? Would you insulate the coop during the winter?)
We just leave them in their normal one, don't need any insulation.