This site seems to have some good references that check out. Appears there is much room for interpretation with "free range" and others. I hope the UK has better regulations that we do in the US.

"The USDA definition of "free-range" is rather vague. In order to label their meat and poultry "free-range or free-roaming", "Producers must demonstrate to the Agency that the poultry has been allowed access to the outside." (1) No mention of vegetation (pasture) is made. Poultry producers themselves seem to have no common standards on what the term means. Some producers interpret "access to the outside" as a small pop-door (chicken door) on an end-wall of a 100 ft. long shed filled with un-caged birds moving about freely on a litter-covered floor. Others feel they are compliant with the spirit of free-range if their birds are outside in the fresh air and sunshine; even if their "range" is bare dirt.

When it comes to the consumer's perception of "free-range", arguably the vision that "free-range" most often conjures is of an un-fenced bird happily hunting and pecking in the grass. Because of the wholesomeness associated with the term "organic", many consumers take for granted that all certified organic poultry raised for meat and eggs are raised outside on green pasture. Sadly, this is not so. The term "free-range" is not even listed in the NOP (National Organic Program) "terms defined."(6) They do give guidelines that say: "All organically raised animals must have access to the outdoors..."(2) So when someone purchases poultry products labeled "free range" or "organic", the birds may never have actually seen the light of day or green grass its entire life. Technically, they simply have to have a door out of their confinement, but they don't have to necessarily walk through that door to meet the requirements."

Edit - adding link: http://pasturedpoultry.org/pasturedpoultry.htm