Re: Billie Piper not involved in 50th anniversary
All four episodes of War Machines still survive, and they're on DVD.:
Be glad there's even that - until 1984, only part 2 of War Machines survived (ditto for Time Meddler). So at one point there were no complete stories for Ben and Polly (or Victoria, come to that. And only 8 episodes at all for the pair. For Victoria there were only two. And no episodes at all for Katarina and Sara).
"Some days are better than others. They say that where I come from."
"Loudly, I imagine, on the day you left."
(Blake's 7 - Rumours of Death)