Many thanks for the feedback - I begin to understand what is going on. But there's something not quite right here somewhere.
My music files are organised on traditional lines - a folder for each artist, with sub-folders for each album. In general, I use the Organise Files function to maintain that structure. My Edit Preferences - Sorting/Grouping settings currently specify that files for each album are organised in their own folder.
I actually have 7 Greatest Hits albums in my library. The first in the list (currently Heart) shows correct values for Album Duration and Album Track count, but the remaining six all show the same erroneous values of 105 tracks and 412:32 duration as previously reported. I still don't quite understand where those values come from, as they are not the correct total for all my Greatest Hits tracks - not even if I exclude the Heart album which seems to be displaying correctly....
If I look at "Artwork" or "Albums and Tracks" views and filter for Greatest Hits, I can see 3 albums. The first album shows the artwork for Eurythmics: Greatest Hits, but includes tracks from both Eurythmics and Fleetwood Mac. The second album shows artwork for Heart: Greatest Hits and (correctly) only includes the tracks from that album. The third entry shows artwork for Linda Ronstadt: Greatest hits, but additionally includes the tracks from Robbie Williams, Shania Twain and Texas.
I don't really understand how this can be - I would expect either that all seven albums would be grouped together as one, or all would be displayed correctly. I haven't yet spotted anything which would make them group as they are currently doing.
If I change my grouping settings so that an album is defined by the fields Album Artist and Album Name, the seven albums are displayed correctly - each with only the correct tracks for that album.
The Album Track Count is now correct for each individual album, but the Album Duration is about 10secs larger than the totals calculated using Library Reports from boroda74's Additional Tagging & Reporting Tools. I'm working on an Excel spreadsheet to help analyse my album durations in the hope of identifying where the discrepancy lies. It's currently taking a bit of time to get right, so I'll report again in due course.
I'm quite happy to keep the new settings identifying my albums by Album Artist and Album Name, but I'm slightly puzzled why the "files in their own folder" option doesn't work as I anticipated. It certainly seemed to be the best match for my current situation.....