Hi Simon, there is a CenterAtOrigin script here: http://moi3d.com/forum/index.php?webtag=MOI&msg=2409.2

Instructions for installing a plug-in are here: http://moi3d.com/wiki/FAQ#Q:_How_do_I_install_a_plug-in_script.3F

That probably doesn't do quite exactly what you want because with multiple objects selected it moves everything as one big block rather than each object individually. But if it does what you need with one object that should not be difficult to modify for you.

Then for the export, do you export all these objects in just one .obj file or do you want something like a separate file for each one?

- Michael