1) The lock barrel in the driver's door only locks and unlocks the driver's door. The central locking only operates from the remote or the button on the dash.
2) I had this on my driver's door, and the dealer's answer was a new lock. Chances are though, if you take the trim off the inside of the door, you'll find a linkage that's broken or just come adrift.
3) If the light is in the boot, then I'd expect it to come on when the boot is opened. It may be a 3 position switch on the light, with the switch needing to be left in the middle for it to work when the boot is opened.
4) Fast flashing on the indicators tells you that one of the bulbs isn't flashing. It normally means the front or rear main bulb - a dead wing repeater isn't usually enough to set it off. It could be a number of things, but the first thing I'd try is taking both bulbs out on that side, and giving the holders a good clean. Edit: Or (with thinking head on now) just wait for the fault, park up, and see which bulb isn't working. That's the culprit.
5) I'm not sure about heated seats. They certainly weren't standard across the range in the UK and neither of my RXE's had them.
6) In the UK, GSF (German, Swedish, French - formerly Andyspares I think) are usually pretty good on price, though I think they tend to concentrate on mechanical components rather than trim. They do international delivery, but don't ask me how much it'll cost.