Forgive me for being such a nuisance but I seem to have hit another wall here, possibly due to my ignorance.
I have managed to get the music type instance working very well, after doing some realigning of categories and tags.
I then created a 'Videos' instance with the object of using another taxonomy exclusively for this instance.
I set the new instance pu exactly as the 'Music Type' instance but now have the following problem.
Under Relevance Options I have selected the available taxonomy as 'post-gallery_videos. (see the first screen shot please)
Under Advanced I have excluded all categories that are not relevant to 'post-gallery_videos'. However, when I try to use the option to select a taxonomy, after I save the system defaults to the Music Type taxonomy.
I look forward to your response.