X5 3.0d Auxiliary heating remote

[Eric Le Baron]

Bought a used X5 last week having option 536 (Auxiliary heating/ventilation).
Switching it on using Direct Mode on the 16:9 display works fine.
However, unable to switch it on using the included remote control (Webasto T70 according to the battery cover).
Is there a receiver module somewhere in the car?
If so, where!
It would help me a lot if I could locate it.
Called a couple of dealers here in The Netherlands but they didn't know.
It's not really a common option for the Dutch....