I stumbled across an additive called coldflow350 which claims to lower the point at which the fuel waxes by stopping the crystals from forming. My fridge test was pretty conclusive as you can see in this video, the first pour is treated and the second isnt :-
It works out pretty cheap as you only need a very small amount. The batch used in the video was mixed for a few minutes at room temperature.
Since this video was made I have been on a trip over to Bruges for the Bruges beer festival using treated veg. We stopped off in Poperinge to visit our favourite beer shop and dropped in on the monks at the Abbey of Saint Sixtus in Westvleteren. They brew some mighty fine beer which can only be obtained by visiting them in person. Well worth the trip though.
Details of the monks and the beer can be found here :-