[dwig]

I'd attack the problem by:

1. Add all of the books, letting them each be separate book entries.
2. Review the metadata for each to choose which has the data you prefer to keep and, if necessary, manually edit its metadata to append any data from the others that you don't want to loose.
3. Select the "best book" by itself and then select each of the others
4. Press "M" to merge them into a single entry; calibre will now do "the heavy lifting" merging the various individual entries into the first selected entry and in doing so will move the files as necessary so all will be in a single folder.