This may also apply to earlier models, but specifically it applies to 2010-12 models. I didn't know that the front and rear armrests and speaker grilles are identical. Thus, I have been able to source a rear o/s door card in very good condition with an unmarked armrest to replace the somewhat worn version on my driver's door.

All you have to do is drill off the heads of the moulded retaining 'plugs' for the armrest and speaker grill (on the back of the door card, so that obviously has to come off) using a countersink (a drill may well go straight through, not recommended), remove the strengthening plate, change them over, blob some epoxy adhesive on the retaining 'plugs,' pop the plate back on and Bob's your uncle. I now have a very nice driver's door armrest! Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII

I've kept the door handles and speaker grilles from some old door cards I was throwing away for the very same reason. Quite a straight forward job to switch over. Tom

Current Drive
2011 4.4 TDV8 Autobiography - Santorini Black - Ivory Leather

Previous Drives
2004 Model Vogue Td6 (Touchscreen) - Java Black - Parchment Leather
1994 RR Classic 3.9 V8 Soft dash - Niagara Grey - Grey Leather
1972 Series III SWB Safari - Green (Hand Painted) - Black Plastic

Took about an hour, and it looks so good!! Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII