I ordered from GB a climate control unit and just when I deployed it on my US car the first time, the display changed from Celsius to Fahrenheit within one minute by itself. I videotaped this feature here

MVI 0306 - YouTube

I think the control changes the temperature display automatically, depending on the car. Now it's F permanently.
I have no experience in the reverse case (from F to C) but I think it has to be the same.

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1996 E320 since 1/16/08, 171K miles as of Feb 2011

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1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE

neat

Could be still in C, just a sign of how fast global warming is advancing