If it is definitely the colour coming off, stick to your guns and don't be fobbed off with 'normal wear' as sometimes happens. It isn't! Let us know how you get on. It will cost you £11 to post the bag in and it will be dealt with far quicker. Keep your postage receipt and email them a copy of it because you should get it refunded along with compensation for the bag. You should not be out of pocket.
I emailed customer service today and they have confirmed they have received my bag and it's now waiting to be reviewed by the Head of Production Quality, that sounds all very official or is that what they normally do ?
This is normal in my experience. Have you asked CS to contact you with his decision?