>> Ok cheers - I had tried changing to GstPlugin and that was ok - but I was
>> hesitant to do this because I assumed the generated boilerplate code is
>> correct, and I had done something wrong.
> I don't think so. IMO, the "make_element" script incorrectly substitutes
> the string "Plugin" with your custom base name here, as the source base
> name for the gstplugin.* template code is "plugin". That replaces
> the GstPlugin type by accident.
Fixed in cvs. Thanks for spotting.

Nice one guys, thank you for fixing ;-)