Normally I'm the one that answers these questions for friends, but my mind has gone blank! 
How does it work if a dog enters a show where the AVNSC class is not restricted to a group and wins?  Are they allowed into the respective group for being unbeaten, or just a pat on the back well done, good for you?  There is an AV open class per group, but was thinking of entering the AVNSC as the classification is so much better.  My gut feeling is entry into the group wouldn't be allowed.
I must add, I'm not expecting to win, but having a rare breed we try and get them in the group as much as possible so that people can discover and learn about the breed.
Any help?!

It would depend on how the schedule is written. They normally state somewhere (possibly in very small print ;-) ) just how they are working it.

The winner of AVNSC should be able to enter the Best in Show or the appropriate group as long as they have remained unbeaten and there is not a breed class of course. Winners of AV are not allowed to go forward unless they are puppies.

AVNSC is the place to go, you could not go any furhter in the AV classes.

Thanks everyone, I had a complete mental block this morning!  As I said, I'm not going expecting to win, but want to enter my girl in the most appropriate class.