Never ever ever stick any part of your body under a car just on a jack. Always axle stands!!
Cam follower - easy to do on a BWA or BYD etc but is a pain on an AXX (banjo bolt), although once you do it once or twice it becomes a lot easier
Diverter Valve - I found it much easier to remove the wheel, remove the arch liner and do it that way, although it can be done without removing anything from underneath - although I imagine its more difficult.
