I hadn't thought about the fact that voice acting is a completely different beast from film acting, and I think you're right, BP doesn't have voice acting chops. It's not so much the accent that made her Rose efforts fall short, it was that she didn't sound young. In "Infamy of the Zaross", there were three female characters and they all sounded the same (I couldn't tell them apart), like the oldest, who was the mother of the other girl and Jackie's contemporary in age. Rose doesn't necessarily need to sound like a chav, but she should not sound like a forty-year old woman.

As far as I know, there isn't any way to find out how sales went. BF doesn't mention that at all, even at Gallifrey One. I'm sure it did well, simply because of the support for that Doctor/companion combo in the fanbase. "Sword of the Chevalier" definitely ranks down with the worst audios I've heard so far, as well as the worst TV episodes (though I admit it didn't enrage me with stupid like "In the Forest of the Night" and "Sleep No More" did). I expect "Infamy of the Zaross" is pretty average, even though I didn't particularly like it.