iOS 8.4 Music App chewed a lot of data while roaming!

I roam on occasions in Europe and so i'm fairly good at switching a lot of unnecessary Apps/Updates/data usage etc off. I noticed yesterday after buying a 50MB data bundle, that after I started listening to my Music, it chewed through 35MB very quickly! Under Cellular/Mobile the App said it used <500KB, but under System Services, I saw that iTunes Accounts indicated 35MB!!!! I immediately turned data off for the App. I have 3000 songs locally on my iPhone 6, I don't use iTunes Match, nor the Radio, nor iCloud with my music or any other streaming option.

Just wondering if anyone else out there has had the same/similar problem, also just a WARNING to people that are going to roam.

I would be interested to know why it used so much data, when it didn't need to access my Account to play music.