I finally solved this problem. Buy a CSR v4.0 enabled bluetooth dongle on ebay, plug it in to a usb slot. Right click the bluetooth icon in system tray and select "Settings" and tick "Allow bluetooth devices to find this computer." Then click "add a device", turn on your bluetooth headphones and the headphones will show up in bluetooth devices. Add the device, then right click your speaker icon in the system tray, select playback devices. From the menu, select the headphones and set them as default. I did this and they work perfectly. Furthermore when I turn the headphones off, the sound goes back to normal speakers - no other adjustments made. Turn the headphones on again and the sound defaults to them. I noticed on an earlier failed install of the headphones when they did appear in Devices and Printers that the drivers were CSR something enabled. I did try some cheaper dongles and the actual Plantronics USB dongle(expensive) to no avail. Get a CSR 4.0 enabled device. Mine cost 6.00AU total.
Note that Windows will detect and automatically install drivers for the device. It also comes with a driver CD.