Ian,

'M' is the indication used by KLM for economy on boarding passes, regardless of fare class.

As for upgrades with miles, in most cases, only fare classes S, X and B are upgradable, with one exception. Flying out of AMS (and JNB), you can buy an upsell, and then upgrade with miles. The cash amount varies according to fare class (I'll have to find the post that has these listed), and V fares are excluded from this.

Some pricing can be found in this thread: http://www.flyertalk.com/forum/showt...ht=jnb+upgrade

Cheers,

GenevaFlyer