I have been on the mobile to someone who might be able help you. he says to give him call when you you've got 10 mins...
He used to work with us at the councils waterside depot, but he's now up at the civic somewhere, but doesn't mind helping if he can
the name is Richard Beale and he is a "Parks and Green Spaces" (laa dy dah! ark at 'im) Officer for SBC, he says to use the office phone 463304 (8 till 4)
i know its a bit useless if your at work but give him a bell he's a top bloke for plant idents etc better than bad stomach ache or worse
i used to work with him when he was just a umble gardener. he used to work with an old italian guy, they were always 'livin off the land', harvesting nuts, berries, apples as they went. He will be able to let you know if its edible.