I should be able to take some clear photograpgs of the bag. I've had other items authenticated in the past and have never used an online service, I guess it's just peace of mind I'm after really. But thank you for your suggestions, I'll check them out first.I don't see why you would need an in person authentication (not that I am aware of such a service), as long as you can take clear photos you could use a service such as Authenticate4u or Fakespotters. Very occasionally, they may suggest a physical inspection but that would be highly unlikely for that item.
Regards