Thanks Jochen. There is no on-screen menu to change the TV settings. I'm not that technical so would not be confident enough to remove the unit from the dash etc to check any 'rear of unit' switches/buttons.It is a factory fitted unit as it shows in the individual factory specs for this particular vehicle & must be a European one, as the graphics (for channel setting etc) are in English. There is a User setting, however, to allow changing between English & Japanese.
This is a picture of the touchscreen: