@cirocco - Thanks for the comments, all input is appreciated around this.
The extra data is easily stripped off with a regex on the author field. And flipping author names is one of those topics that gives me continuous grief - however I would just apply the same approach that I added to the calibre metadata download options dialog of a "Swap author names from FN LN to LN, FN" checkbox. So you can decide at the time you tick the fields whether to flip it or not. The authors column in the Resolve grid is currently editable only for empty books, I could loosen that restriction. So if the automatic name swapping doesn't guess it right (it is impossible to correctly handle all cases) you can manually type the correct name. Or you can wait until you click Finish on the wizard and the books are displayed in the library, and fix them there.