This is prob a simple yes or no answer. Im pretty sure i know the answer but seek confirmation for piece of mind. If your playing in the key of C, must you stick with the usual method ie C= M, D=m, E=m etc or can you swing it round whilst remaining in the Scale of C and play in A Aeolin therefore A=M, B=m, C=m.

Also whilst at it. When menthioning what key i was in (say for A Aeolin), would you say key of C follow ed by A aeolin, or simply A Aeolin without mention key (seeing they would know its C).
If you are playing in A aeolin mode, then the chords are still the same as in C major, i.e Am, C, Dm, Em, F, G, B dim, the only difference is that you are starting on the minor, or aeolin, but the chords/notes remain the same.

You call call i either, they're both the same.