I kept for many years, Warren Hybrid hen's, they are hard to beat for pure laying ability, I also kept and bred Old English large game birds, they were far different to the warrens, I even manage by accident to cross a Old English game with the warren, produced some fantastic looking birds. just make sure they are secure in the night and their pen is fox proof, because foxes are so numerous now and Urban foxes show less fear than their country brothers and sisters, be warned though be as clean as possible, and dont throw to much food around, dont want to invite Mr Rat around for lunch!
Best of luck.
Jamie.