The "known flaw" would seem to have been corrected on your PCN. The case you cite was 2 years ago. As far as I can see the two 28 day periods are now correct, although this is just a quick trawl through it. Be ware that if you go down this route, you'll have to take them to Lonon Tribunals and risk the full PCN penalty.
Why on earth did you driver make a U-turn right by the sign, when there is another sign indicating a mini-roundabout a little bit further on where the driver could have turned round ?