In my E53, I came down from the MID unit on the right side of the driveline hump, into the front right edge of the centre console just above the carpet, and then back to the cupholders. It was very straightforward.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue