Does Caratacus count as Keltoi anyway? :P
But yeh, I agree with Brennus. He would rather be called a Roman if I remember correctly.
Also, I wouldn't call Solduros bodyguards. They're called "Devoted ones" for their oaths to each other, beyond that we don't know much about what roles they would have performed. That's the most unfortunate, yet enticing part of the Keltoi, how very little information we have about them, and most of that from their enemies.