I'm asking this question for a mate who's borrowed a 2007 RRS 2.7 TDv6. The on-board computer is showing up a warning of low coolant level, when started, where about in the engine bay is the tank located.
I'm guessing it's sorted by now, but I'd be surprised if there's not a picture of it in the handbook. Which assumes the handbook is still in the car, of course....