Is there a way to force all styles and reference definitions to be grouped within an object?  I run into problems when copy/pasting across documents that the styles don't always get transferred, or conflict with ones already there. This results in items having the wrong colours, and other attributes.  I'm hoping for an easy easy to somehow compartmentalize an object so it's safe for copy and paste.

I believe it's holding shift+cmd+V (on Mac) while pasting attributes between documents and objects. Not sure about the equivalent of the "cmd" key on PC.

I'm not looking to copy only attributes, I want the styles and everything to be copied along with the object to the other document. It seems that Inkscape quite often loose track of styles when pasting between documents.

What you're calling "Styles" I may ask?

Everything needed to make the pasted element look the same as the source element. That would be styles, attributes, defs, etc.