ITunes For Mac :: Automatically Changing Edited Song And Album Information?

I've got a pretty big collection of music on iTunes - almost 1000 albums - and I'm pretty anal about the way it's stored and managed and I regularly change the song and album information to suit my own "house style". All my music was stored on a Dell laptop and was fine - I had no problems with changing and editing the information. I recently bought a MacBook Pro and shifted all the music files from the old machine onto the new one (a lengthy and frustrating process) and since then, I've had a lot of hassle in terms of amending and organising my iTunes collection. A lot of the music I've purchased from the iTunes store has reverted back to its original state, no matter how many times I've changed it. 

For example: 

Lana Del Rey's Born to Die (Deluxe Version). I've removed the "Deluxe Version" from the title but I quit iTunes or sync it with my iPod, it automatically adds it back. I've changed the information in the song info, I've even changed it in the sort info just to be sure, but it always changes back. 

The same with the Anthems Electronic 80s compilation. I want to call it Ministry of Sound: Electronic 80s and remove it from Various Artists (by deleting the album artist from the information). But after iTunes is quit or its been synced, the same thing happens. It appears as two albums on my iPod - a handful of tracks appear under the old title while the bulk of them appear under the new one. 

It's happening across loads of albums, all ones I've downloaded (the stuff ripped from CDs seems to be okay). I've done as much as I can in terms of the song info but no matter what I do, it just reverts back when the programme's quit or I sync my iPod. I don't know if it's anything to do with the fact they're in the Cloud or they've been imported from a Dell laptop or there's an underlying problem with iTunes ...