What would be typical holdings for a noble's officers? Specifically I have a character who is the heir apparent of the Marshall of Caer Colun. Would dear old dad be a simple landed vassal or would his position indicate that he is a banneret?

Cliff

It is my understanding that the officer serves at the noble's pleasure, and can be just a trusted household knight to ensure that he has no other obligations to distract him. Of course, such a trusted man is often married off to a heiress as a reward for good service, so lands wouldn't be out of the question.

I'd leave it up to the GM. What works in your campaign? Do you want him to inherit a banneretcy in his own right? Are the rest of the PKs humble vassal knights? (Of course, the lands of teh dear old dad would presumably be near Caer Colun, meaning trouble in the years to come.)

Remember as well that the position may be rewarded with life tenancies or even office tenancies i.e.
1) land and/or dues (I have things like income from Mills or Salt pans or bridge tolls) that is awarded to the Marshall for life. Upon his death it will revert to the Lord to parcel out again as he sees fit.
2) Likewise things that are awarded to the Marshall whilst he is in post. When he gets replaced or retired then these may pass to the new Marshall.

Lastly, remember that the post of Marshall is most likely non heriditary. (Posts can be hereditary but in my view any sensible Lord only lets that occur with non critical posts like Cup bearer).

Chris