In p. 341 it says: "King Cerdic the Saxon (well treated by Arthur) might appear", but nowhere else does it say that Cerdic keeps any land or holds any position under Arthur; he just disappears after being taken captive at Badon. The context of the above blurb implies that not only is Cerdic hale and hearty, he also has a significant chunk of his kingdom of Wessex left. And that he would be willing to fight for Arthur, too. Given that this is in no way mentioned or even implied anywhere else, I would be happier to just remove that throwaway comment completely.

Furthermore, Cerdic at this stage (year 555), is AT BEST 87 (Vortigern dies in 468) or even 105 (Vortigern marries Rowena in 450). Given that he had an adult son (Cynric, early 20s) already in 496, he was probably born in early 450s, making him over 100 years old...

EDIT: In Cerdic's character sheet in p. 16 of Gamemaster Characters section of GPC, his birth year is given as 461 and his age 35. He must have been one heck of a precocious lad of 13 or so, to have a son in early 20s in 496! (Not impossible, though, for a young, lusty princeling, although a bastard would be more likely than a new prince.) I'd rather make Cerdic 5-10 years older than this.