If you wish to use bluetooth headphones and the internal speakers then you need to do the following.
First pair the bluetooth headset to ensure the TV has it listed in its available devices
Press and hold cog button on remote for 5 Sec
Select Sound
Select Sound Out
Scroll down to Bluetooth and select the "Device list" on the right
If not already searching press the search button
Switch on your bluetooth headset in pairing mode.
Select your device when it pops up.
Go to the Sound configuration menue
Scroll down to "Bluetooth Surroundsound + Internal TV Speakers"
Click on the device list on the right
Select your bluetooth headset.
Exit from the screen
Job Done