OK. So today I added Bluetooth to the S40. The car came with a factory AUX port, so this made things easy. I picked up the Sony RM-X7BT In-Car Bluetooth Commander cheap from JB-HiFi.
It comes in two parts -
1. The Bluetooth adapter, powered via USB, and
2. the remote Commander wheel, used for pairing phone via NFC, map zooming in and out (Waze), volume control, seeking tracks, play/pause and answer calls.
It works well. I tried to mount it where I had room while trying to maintain the simple aesthetics of the interior. The remote wheel was a challenge but centre of air vents was the best place.
I ran an AUX extension cable along the driver's side of the centre console to the front dash, mounted the input jack just under the dash next to the waterfall control panel. Tucked the extension cable in the sides of the waterfall panel. Ran the supplied AUX cable from the Bluetooth adaptor on the left behind the waterfall panel across to the extended AUX input jack on the right of the waterfall panel, then tucked the loose cable up behind the waterfall panel and dash, so all nice and neat. I then ran the cable supplying power to the Bluetooth adapter from the rear 12 volt accessory socket via a USB 12-volt adapter plug, along the passenger side of the centre console, tucked it in the side of the waterfall panel up to the Bluetooth adapter. Keeps the cable neat and out of the way.
Long term plan:
1. Run the AUX cable underneath the centre console so it comes out behind the waterfall panel.
2. Mount the Bluetooth adapter on the roof lamp housing. Would look more factory-ish IMO. Just need to work out getting USB power to it. Pulled out the roof lamp housing and found that there's a wiring harness running above it in the roof, so assume I could take power from there somewhere. But that's another project.
Any how here's what it looks like.