Thanks for the information Adam, I've just managed to get back to this now and will give it some more effort.
I understand the info to mean that I need not change anything from the provider defaults and the editor will use the default.css, skin.css and portal.css for the dropdown and will also use the same sheets in the editor area. Is that correct?
I've not yet changed the defaults and I can see that the Css Class dropdown has just a handful of classes on it (normal, head, subhead etc). They are useful classes and they appear to be correct for the skin.css, but I'm surprised it only shows these few when the skin and default css files contain many more classes. Is it only choosing to display a few on purpose.. and if it is, then is this a setting somewhere?
Also, in order to get the editor area to always use the correct skin.css and the portal.css that is associated with the current portal, what would go in the EditorWysiwygModeCss. I think the example given implies that the editor area style sheets aren't loaded dynamically according to the current skin location.. is that correct? It would mean that only one portal gets a wysiwyg view and the other portals share that?
Thanks for all the info
Rob