Not having much of a clue (yet) how Steam Locos work, I assume that if the headshunt results in the engine being at the front, but still facing into the platform, it can still move forward ok i.e. the engine doesn't need to be pointing the direction it's going (as in the Sidmouth pic)
http://www.disused-stations.org.uk/s/sidmouth/sidmouth(tarr8.1963)old3.jpg