I have a 6 month old beardie who's lovely white face is becoming stained around her mouth. (She is a bit a of a chewer). Is this common and will it improve once she's through her chewing stage? Is there anything I can do to reduce the staining?

Most Bearded Collies tend to get this type of staining and there isnt a lot you can do about it.  If you are showing your dog you can get special quick spray shampoos that will clean the area but it will be back with the next meal or when the dogs hair gets caught in its mouth.  Some owners recomend brushing in potato flour and then brusing it out again but the same thing goes it will be back with the next meal if your pup is prone to this kind of staining.

The best thing I find is to clean my dogs up when I want them to look perfect white and to leave au natural when it isnt essential.

Good luck with your new puppy.

I agree with other post nothing you can really do other than to keep it clean.
good luck with your Beardie wonderful dogs one of mine is nearly 6months too