Hmm doesn't seem to work...
Strangely it does show the track in the status bar and the widget shows the pause button, meaning that it thinks that it is playing.
If I press the pause button, the button does not change, but the music starts playing.
Then pressing the pause button again actually pauses it!
I have managed to work around this by using an app called AutoMate.
I have set a routine that runs automatically as follows:
Startup - Wait for boot routine completion - 5 second delay - Is music playing - (No - Press play) (Yes - Return to step 2)
This seems to work every time on my test phone, so I expect it to work on my car stereo
That said, it would make life easier if it just worked.
When I set it up on my stereo, I will try without AutoMate first, as it may just be an issue with the phone.
Thanks for your help!