For me just a couple of things the white triangle in the top left looks a little odd, is it supposed to be the page curling over? - also I think you should give the taps on the nav a roll over effect, perhaps so they jump up or down on hover...
I particuarly like the subtle gradient on the top left of the body as a light source!
Maybe your form elements could be jazzed up a little to be more in keeping with the site, the contact form and search box seems a bit like the sites been designed without theses then they've been added in after the build/design, maybe green borders around the input boxes and a nice submit/search button?
I like that funny worm in footer
And like others said, this triangle looks weird, for me you could the top of this container make in some angle like buttons (buttons for me looks fine )
The rest looks great
Same as above in terms of the 'fold over' (if that's what it's supposed to be); it's not quite there. Same goes for the triangles on the images/links which break up the body text.
One other point is the Whats Organic .co.uk header in the top left. I know it's a reference to the URL which doesn't have an apostrophe, but not having an apostrophe here looks like a mistake to me. It's more of a header/title than a URL (I know it's both, but you know what I mean), so for me it should include it.
P.S. Love the the language used for the site credits.