I too know the area (or at least i think i do - despite what my profile says) as i live and work up there during the week, and with the notorious housing estates nearby it comes as no suprise to see people fishing there in the close season.
Good on you for taking the pics, though it'd be a brave man from the EA who approaches a large group like that on his own. Sadly, unless you fancy a swim, I think the EA would need to go mob handed to challenge and sort these "people" out, but the chances of that happening are probably slim. As frustrating as it is I don't think there's much we as anglers can do about such people without compromising our personal safety.