If you have the eMyWay unit (with the blutetooth logo on the front) like this one:

- eMyWay citroen bluetooth radio and sat anv
The manual seems to suggest it should be possible to set your phone (S5) to act as streaming source over bluetooth to the eMyWay.
from the Citroen Manual wrote:AUDIO STREAMING
Streaming allows audio files on your telephone to be played via the vehicle's speakers.
Connect the telephone: see "USING THE TELEPHONE".
Select "Audio" or "All" profile. If play does not start automatically, it may be necessary to start the audio playback from the Telephone.
Control is from the peripheral device or by using the audio system buttons. Once connected in streaming mode, the telephone is considered to be a media source.
It is recommended that you activate "Repeat" on the Blue tooth peripheral
Missing Lincs wrote:Bluetooth for phone and Bluetooth audio are two separate things,
You need to set which option is required when pairing your phone.
from the Citroen Manual wrote:
USING THE TELEPHONE
The system offers to connect the telephone: in "Hands-free mode" (telephone only), in "Audio" mode (streaming: playing music files on the telephone), or "All" (for selection of both modes). Select "OK" and confirm