I gave you the arithmetic, but forgot to mention that the council's second 28 days is from the date of cancellation of the first PCN. So I think you do have a second string to your representations bow of "PCN served out of time". The council will then have to explain their tardiness in serving the second PCN. It's not a slam-dunk argument, though, just another hoop for them to jump through !
I always say make the bug***s do at least some work !!