Marc1

I can't be too specific without your VIN, but the 'USB Box' is an available accessory, so would likely be connected to the CD changer outlet at the rear of your RD4 Head Unit. Most of the Factory fitted USB ports (like the Navidrive 3D system that I have) have a dedicated USB port that is located in the centre armrest, below the diagnostic port. This would normally be wired up to the back of the Head Unit. So you would likely have to see what connections you have at the back of your RD4 first. The RCA connector located in the glovebox isn't really that good for audio and doesn't provide any track information IIRC.

Does the cruise control apply the brakes if, say, going down hill? (It certainly doesn't on my Facelift.) The C5 doesn't have the 'active cruise control' with distance monitoring, so will not apply brakes to maintain distance - it only uses the acceleration / deceleration as in previous C5s.

No, none of the C5s have a heated front windscreen with heating elements within the glass.

Yes, this is normal - the switch will illuminate and a message will be displayed on the screen. It doesn't stay recessed when activated.

Like a numpty, I forgot to set up alerts, so have only just seen this - here's the link to the ones I bought anyway Pete: http://www.ebay.co.uk/itm/HP24W-G4-13mm-DRL-HIGH-POWER-LED-SMD-BULBS-CAN-BUS-fit-CITROEN-PEUGEOT-/310873482871?hash=item486180e677:g:rQ4AAOxyYSdS~Olk

I've replaced my C5 X7 DRLs with LEDs after a Filament bulb failed. Contrary to what has been said in some earlier posts, I certainly would not recommend any sort of domestic Halogen bulbs! They are not suited to the fitment and application of the DRL housing and plastic, as they will generate far too much heat. People who have done this have ended up paying for a new light housing as it melted! As the DRL had not been changed before, the fitting was very tight and I paid Citroen to remove them for me at a cost of about £40. I ordered some LED 7.5W bulbs, which are the brightest ones available and have the 2 prongs. I carefully removed the old bulbs from the bulb housing and inserted the new LEDs. I amply greased the plastic seal at the base of the bulb holder and also drilled a small hole through the blade of the bulb holder. Through this, I threaded a small plastic cable tie and made a ring. Placing my finger through the cable tie loop, this ensured that the bulb and holder remained in position and would not fall down into the housing. I manoeuvred the bulb into the housing and then used the cable tie to turn the thread a quarter turn - the grease now making it very easy to do without the torx. Job done. Because of the ring pulls I made, if I ever want to replace or change them again, it will be very easy to do so. :)