We got the Eglu cube which is large enough for up to 10 chickens, although we only have 3 at present - to be increased in due course. It is also fox-proof with the anti-dig skirt around the edge (which you can't see in the pictures as I've buried it under the gravel).
We were advised against using bark because it quickly goes rancid in wet weather. If the run is not covered it is better to get wood chips (from the local tree surgeon). If you cover the run, which I do, then horse bedding of various sorts is good - I use Hemcore, but there are others such as Easibed and Aubiose that do the job too. I also put the Hemcore in the poo trays (dries it out, makes it easier to empty) and nest box. I line the run, nest box and poo trays with Stalosan F disinfectant to kill parasites and worm eggs. Also worm them monthly with Verm-X and three monthly with Flubenvet.
We decided on the Eglu after visiting a few chicken-keepers. The wooden ones tend to smell bad and you have to spend such a lot of time cleaning them to prevent this. The plastic ones tend to be easier to clean and don't have crevices for the red mite to live in.
However we are thinking of building a walk-in run on the same site later in the year, as we'd like to add a couple more chooks to the collection. They get to free-range virtually every day anyway whenever we are at home.
I went on a half-day chicken-keeping course and it was very useful as I picked up a lot of tips.
Lots of gratuitous pictures
Here. This is our set-up
And again
And being spoilt
