:) Thanks for all the replies...
Hen house/coop is now ordered! No luck finding a second hand one locally and they were going for silly money on eBay so decided to buy one in the end... Saw one I liked for a good price so decided to go for it :)
This is the house/coop I have ordered:
(http://www.ideas-4-pets.com/articles/wp-content/uploads/2008/02/covered-chicken-cottage-ii_crop.jpg)
(http://www.ideas-4-pets.com/images/large/RS709_crop_04_LRG.jpg)
Still a fare bit of work to do before I go and pick up some hens i.e. Level off the area, Lay the paving slab edging and put the coop together. Extension to the pen will be done after I'm up and running as I need to wait for the next pay day before I spend anymore money on the allotment LOL.
Barlbylofts: It's funny how the rule 'No Livestock' can differ depending on the allotment, our rules state: No Livestock may be kept on allotment site *With the exception of Hens & Rabbits.
I think this is because they used to be kept more often for food in towns and cities and therefor are not classed as pets. Might be worth you checking what you site owners class as "Livestock"... Just a thought.
Cheers,
IsleworthTW7