Aircraft approach categories
 

Sorry if this has been asked before, but I am not too good at the search function.
If an approach has different cat1 minima for catC and D and the aircraft falls in both categories depending on flap used. Is it as simple as using the appopriate speed category or does the highest apply?

CATI?
 

As CAT I applies to ILS approaches, the minima are the same for all aircraft. That also applies for CAT II and III. At least in my part of the world.

You would use the one appropriate for the speed, unless company SOPs say otherwise.