Various Artist - sorting problems iTunes

So i have a huge library of compilation albums, some are identified correctly in terms of song name, artists name, album name, and the 'album is a compilation of songs by various artists' ticked. HOWEVER

the vast majority of them simply have Various Artists, or Various where in many cases the actual artist name is part of the file name (if that makes sense).

The issue I have, when using iTunes 12.x is when I use the 'artist' list, the 'various artists' doesn't put all albums under that single grouping, but rather, it randomly picks albums, or in some cases only parts of the album, and lists each item individually, so my 'artist view list' in iTunes is enormous.

I've mucked about with the 'info/sorting' tab a lot, but in many cases it just reverts back after I click OK.

I believe changing data in the iTunes 'info' window doesn't actually change metadata in the files themselves, so it is likely this metadata that is the problem?

If anyone has a solution - it is getting really boring having this huge list, and having to hunt for a complete compilation album because iTunes scatters it's various parts under all sorts of groupings.