[ Ref 011113 MMDigest, Tommy Forney: Hand-Cranked Player Piano ]

Yes, I saw "The Cazalets" episode with the mechanical piano, too.  It's
a barrel piano (or, as frequently called in the U.K.: "barrel organ").

Unfortunately, while the piano was genuine, its music was synthetic.
If you search the Internet under "barrel piano", you'll see some
photos.  These are pianos operated by a hand-turned pinned barrel.

Other barrel pianos were spring or weight driven, but these were for
indoor, coin-op use.  They were rented out by the day to "organ grinders"
in London, New York and other cities.

They didn't hold a tuning long, as they had no iron plates for stability,
due to the extra weight involved.  They played 10 tunes (changed
according to popular taste), each one revolution of the large cylinder.

Several early cylinder and disc records feature barrel pianos.  They
are fairly musical when in tune, which they rarely are!

Philip Jamison