Heres another link that includes some interesting stuff about upsizing your hoses in order to increase coolant capacity quite significantly, which could be almost as beneficial (and less technically challenging too!).
I don't know about the "25mm over 19mm" sizing on the Terrano, but if anyone can be bothered to check in this weather it would be interesting to know....sounds an easy mod to do, especially if your existing hoses are a bit long in the tooth....