I use a escort van myself and i,m using wfp trolley system , i carry 250l water in 25l barrels plus my trad gear and it all fits in ok , but i,m now at a point where i may take someone on to help and i may need a bigger van i havn,t really thought this through as of yet . I bought the escort because it was a good buy at the time and it has been a good van but in hindsight something bigger would have been better for the long run.
My advice if you are going to go wfp buy a tidy size van first as last...
darren