It never occurred to me that I could import the songs from what I perceived as the main game into one of the adjunct games. From the looks of the site the games that support imported, and importing, songs are GH5/ Band Hero (basically the same game) and GH:WOR. Songs can not be imported down a gaming generation, so GH:WOR can not be imported into anything but GH:WOR can easily read songs that have been imported into earlier games.
The generations seem to be:
1st Gen: Guitar Hero World Tour. (Can be imported into GH5/BH)
2cd Gen: Smash Hits, Metallica, GH5/ Band Hero. (Songs from SH and Metallica can be exported into GH5/BH, GH5 and BH can import into one another)
3rd Gen: GH:Warriors of Rock. (Accepts imports from all earlier games)
The stores for GH5 and Band Hero still seem to be working fine alowing easy purchase of the import licenses. Also Band Hero can be picked up new for less than the second hand price.
Hopefully this will help someone who has been as daft as myself.