This is one of those Homer Simpson “doh!” moments.
After posting I realised I was talking about the wrong preset group.
The Cinema Pro presets operate like any other preset – Drop on to a video layer.
The other preset group was one I downloaded from the Adobe Exchange and simply requires the preset to drop onto the comp window BUT NOT the layer. So it creates a new animated Shape layer.
DOH!
Gribble
::: Time flies like an arrow but fruit flies like a banana :::