[Raven81]

On looking at that article I calculate my hens are meant to have 10 metres squared each?
 I calculated by:
1 acre = 4046 metres square,
4046/400= 10 metres square,
10*4= 40, hence my garden would need to be 40 metres squared.
Any ideas anyone? Am I caluculating wrongly?

Edited to add that I want my hens to have the best life possible, and they are allowed to free range every day when supervised and the rest of the time always have access to their run!

[joyfull]

this is only if you want to sell your eggs as free range (and a good proportion of that space must be covered in vegetation). Most back yard keepers do not meet this, I am lucky I have half an acre (for about 60 chickens - a mixture of large fowl and bantams) plus mine also go down the bridleway and in the local fields.

[Raven81]

Thats ok then! I should have read it properly to start with!! 
So they wouldn't be classed as free range but they're certainly not battery either!!   
Mind you, I don't sell the eggs at all!!