I was messaging with a fellow Pug owner (405 SRDT) in another thread and he said a mate of his gave him a drive in a new Golf diesel. He said it drives like an "F1" car compared to the ageing 405.
Timothy did the dealer show you the warranty statement that says using BD will void your warranty, or did he just say it? What concentration does VW consider as a "warranty voiding" concentration...B5, B20, B50, B100???
It looks like the major diesel fuel suppliers wil be using 5% Biodiesel (B5) in their ultra low sulphur fuels as a lubricant so you probably won't be able to avoid some contact during the warranty period.