1) Licence plate lights needed to be CAN-bus, and this sorted the flickering issue. Since I was already in the shop, installed similar CAN-bus leds to all interior light-domes. From what I can gather, C5 does not actually require CAN-bus LEDs, but it certainly helps when one or two of the bulbs turn to LEDs
2) As for the side mirrors, I think this is a whole new ballgame, the only option is to buy original Citroen mirrors, and the only way that these will work properly is if all the necessary wiring is present and BSI is programmed correctly. Seems like an awfull lot of work and tinkering, and the end result is not 100% quaranteed it'll work. The interior mirror is much, much simpler, it's as close to plug-n-play as you can get.
3) As for the "how-to", it's really so simple you don't actually need any car-related experience to install this. Mirror snaps onto the original bracket which is glued to the windshield (that's why its crucial you order the correct bracket), camera snaps into one of the licence plate-lights holes, and the wiring goes underneath the carpet beneath the bonnet, into the passenger area through the hole for the bonnet hinge, underneath the rubber edge insulator on the sills (or on the corresponding rubber on the roof edge) and into the roof console, where you can also get the necessary switched +12V. Please note that, for 100% correct operation, you need both the video cable and the reverse-light signal cable to run from the trunk to the mirror. All in all, about 30 minutes of work if you are somewhat familiar with basic tools and simple electrical connections.
think the boat can fall off 
