Blue tooth audio streaming

Having heaps of problems with apple music. Its suddenly decided I'm no longer a subscribed after the iPad tells me to take out a subscription, then tells me I'm already a member. When it comes to apple music, 'it just works' does not spring to mind. But that aside.

I am trying to listen to music via bluetooth headphones and speakers, but the music constantly drops out out and stutters. Seems to work fine via internal speakers. Tried three seperate bluetooth speakers - all stutter to the point where its unusable. I'm using a late 2012 iMac with 'el capitan' (os x 10.11) installed.

Any ideas?