Well, I have eaten a number of free-range cockerels in my time, Fi, and the secret, I think, is to hang the boys for a day or two and then do a long slow cook to tenderise and soften all gristley tendony bits.  Roasting or grilling won't work, nor will a stove-top quick casserole or curry.  But there's no reason warrens should be any less tasty than any other breed.