Hiya Ian, welcome to the forum.
Commercial biodiesel is always bit of an unknown regarding completeness of conversion, soap and water content, all of which have an effect.
The 1.9 Kangoo can have either a Bosch injection pump (tough) or Lucas (weak) - it'd be worth taking a photo of it if possible so we can help you identify it.
With the Bosch pump you'll get away with poor quality fuel but the Lucas will break if it's too thick.
As for winterising biodiesel, you're right that in this weather it tends to form waxes very readily, this depends on the oil type the biodiesel was made from.
Mixing with diesel does help keep it thin, but doesn't guarantee it won't form some waxes which could block your fuel filter. The best thing to do would be to make sure you carry a spare filter with you and the tools to change it, if you do decide to go down the biodiesel route.
Given the age of your vehicle (post-1994) there shouldn't be anything in the fuel system which will rot, with the possible exception of the injector leak-off pipes - keep an eye on them!
