If you've had a credit check with VW finance and been properly quoted by VWFS, you'll get the 0% deal, they won't withdraw it - they've made that offer to you.
However, if the dealership has just punched some numbers into their computer as an illustration, VWFS have not offered you finance on those terms and so if it is pulled before you do the proper credit check, you won't get it.
Something similar happened to me when I ordered my R in Sept 2014. Finance wasn't finalised by dealership when GFV was £18.5k, it later dropped to £15.5k and it meant PCP terms were £80pm more with no access to the earlier deal.