Over here (not sure its the same over there) they have 14 days to issue notice otherwise its null and not valid
think it's 3 months... bottom line is if you contest it it's court and double points and fine if the judge is in a bad mood, and it's not like I wasnt speeding, yet if it was a few km/h over the speedlimit. at least I wasnt unlucky in getting 10 penalty points over the course of a week like my mate did , he didnt know that a ccamera van took photos of him daily...