Looking for cheapest optioon whether to take us and Doblo or Mercedes Vito and find someone to share. Does anyone know if a Vito Dualiner is classed as a van or car. Its a lwb but has all seats etc

I think if it has seats & windows you can class it has a mini-bus, the most important thing with a ferry company is that the length is declared correct, if you say its shorter than it is they can refuse travel, they need to make sure they can fit everyone in.
Phone & ask if you are not sure is always the best way :)