I mentioned this in the Trips section a couple of weeks ago whilst having a moan about the current Avanti First Class experience:
It's worth reporting the follow-up. Sat quietly enjoying my journey when upon leaving Wolverhampton the new Guard announces that he is about to come through checking tickets. He explicitly states if you are sitting in Standard Premium please have a payment of fifteen pounds ready, there is a charge for sitting there. He is quite insistent upon getting this message across - so much so that I begin to feel uneasy if I should be in there, First Class ticket or not!
Common sense tells me that I should be valid, but whenever did common sense come into it?
I decide to remove all doubt by moving forward back into the First Class proper. Who knows I might even get another small bottle of Becks?
At the door, I bump into the Guard who of course wants to see my ticket. I explain the situation, fully expecting him to say "No, you're all right, mate. Stay where you are."
Not a bit of it. "You're best off in the Front two," he says.
Now he may have just been desirous that I didn't miss out on that second bottle of Becks. But he certainly didn't confirm that my ticket was valid in Premium.