new chickens

Have you considered a shed? Try the local shed company's as the guy I had my new shed from gives away the old ones he takes down. they are free to collect as it is cheaper to give them away, than pay the local tip people as they charge businesses for disposal! They are very popular with people who have allotments and chickens. With a bit of DIY you can make a very good sound coop. The biggest cost out lay would be for some quality Fox proof weld mesh for the run. Personally I would not economize on this as allotments attract Fox's like you would not believe, and being greated with the carnage after an attack is devestating.

check with your allotment about rules about keeping hens. Mine restricted the amount. Think about time for visiting them 2 times a day, more in winter...disposal of straw, rat and fox protection and costs involved.
Cost up underground protection from rats/foxes/house/run/metal bin for food storage/food costs/feeders/price of hens. Initial outlay could be £500 plus. would you need 4 eggs a day? factor in driving costs if applicable.