To get back to helping sort the problem, I'd quote the DCC development plan item (see above) to him directly (politely). Just because he doesn't need planning permission doesn't mean he shouldn't follow the same rules as someone who does. If that doesn't work, I'd contact the council directly (but let him know you're doing this beforehand). Basically, keep it polite but firm, and let him know what you're doing: that way he can't complain he didn't know.
I'm totally on your side, by the way, as I'm sure most reasonable people would be.