Unfortunately a lot of what you have suffered is not unusual. From the description of the white smoke and a longer crank time that certainly points at injectors and even more so glowplugs as it's probably unburnt fuel. Your plugs will be getting more use because of the colder climate

I haven't had the inject/glowplug issues, but have had both mirrors, tailgate lock mechanism, steering hoses, starter, fuel pump relay, and the entire auto transmission rebuilt, along with a new transmission computer, and I haven't done 47,000 miles yet!! My E53 is a March 05 like yours and I've had it from new.

If you get a bad one, then this happens but it is rare to all of these problems though as I said not unusual. My car was actually built at Xmas 2004 though whether that was significant is questionable. I now have an extended warranty which though expensive is much cheaper than a new gearbox would have been!!

It's also just had a new battery (about the right time) and now needs new brake linings (again about the right time).

I now run an E71 as well and am hoping that will be a lot better - even if someone did reverse into me in a Supermarket car park on Xmas Eve meaning I am now having to have a new rear bumper at 6 weeks and 900 miles of ownership!!!

__________________
Me:
Current: 2011 E71 40D Vermilion Red/Beige Nappa

Wifey:
Current: 2012 R80 Countryman SDX Green/Cream