Go for the 310 or 330.The mk8 is a relatively heavy van anyway, so your load carrying capacity will be very limited with a GVM of 2900 kg.
And yes go for the 155 engine. I find it quite adequate, so I think I would feel the van was under-powered with anything else.
One thing - only what I heard but all the engines are exactly the same bar the software map, hence you may be able to save a lot of money by buying the lowest power and getting a remap right up to 200 bhp...
http://www.ecovehicletuning.co.uk/vehic ... 4/stage-3/ I would definitely get this verified as correct before making a decision though!