Yes I use it Dunc, although i'm over the pond!
We don't have to buy the music here, just add whatever to your playlist/s and you can listen to them on your phone, laptop etc...
I don't know if there is different stipulations in different Countries?
I've just joined Amazon Prime 2 days ago, granted mainly for the forthcoming Grand Tour episodes starting on 18th November with Jeremy Clarkson and his crazy partners, but I had a shufties around the site last night. Looks good, and the filums can be watched without purchasing it seems.
The music?
You say that it can be downloaded onto a personal playlist. Can it then be transferred onto a memory stick or SD card that I can use in my car do you know?