All that is known/theorised seems to be gathered here :-
http://www.whitedragon.org.uk/articles/redhorse.htm

Pics/photos and details of the different versions http://www.hows.org.uk/personal/hillfigs/lost/tysoe.htm

Excavation history
http://www.hows.org.uk/personal/hillfigs/lost/tysoe/tysoe.htm