Ter2blend camera script problem

I originally posted this in Python & Plugins but it got very few views so I deleted and reposted here… hope that’s ok.

I have an animation set up with ter2blend. The problem is that the landscape mesh and background image don’t line up. I know there is a problem with camera banking for the camera script - but I have tried entering the camera/target positions manually and the result is exactly the same.
The camera in Blender is set to 22.7 and the zoom is 1.0 in Terragen. The terrain mesh is the correct size and in the correct position. So… I’m at a loss. Anyone know what might be going on ?
Occaisionally I see the terrain/image don’t quite line up, but there’s normally a very close match - here there is a wide discreprancy. I need a better match otherwise I get very strange results using Blender water to reflect terragen land (see https://blenderartists.org/forum/viewtopic.php?t=27080).
I have uploaded the .blend, .tgs script, and background image. 1.4mb zipped :

Does anyone have any ideas ? I’ve rendered 759 Terragen frames. It’d be a shame if they were all useless.

probably a silly question, but you used terrain units right?

That’s a sensible question, but yes I did.