oh, and a bit more info before i forget.
you will have the choice of a T28, T30 or T32 variant.. these relate to the maximum load... i have a T28, but given the choice again, I would go for the T30 for that extra 200kgs potential.
be wary if you go for a t32 as they require a different MOT (no biggy, but worth bearing in mind) and they are more of a pain to customise in terms of alloys and suspension as they require much firmer springs.
if you do go down the customising route (which you will), be mindful that whilst you can throw on any funky wheels (right up to 22") and tyres, the most reliable performance will be gained from using van-rated wheels and tyres. This means you will normally have less options and will struggle to get over 18". Many people use Range Rover alloys nowadays and I guess those are heavy cars so you should be okay.
don't get too hung up over the engine either... you will be looking at a 1.9 or a 2.5... both have their +'s and -'s. I went for a very basic 86hp 1.9... for £250.00, I had this remapped to provide a solid 135hp, an extra 110Nm or torque (from 200 to 310) and improved fuel economy. what this basically means is don't bother pay more for a more powerful 1.9 variant as they will not be remapped any further than the basic 86hp (as it's the essentially the same engine). the 2.5 will give you a 6-speed gearbox which can be nice on cruises.
in terms of spec... electric windows are nice to have, but can be added for about £150, as can cruise control. air-con would be very expensive to add, so if you want this, hunt out a van that has it.
if you fancy the colour-coded look, do bear in mind that it can be easily upwards of £500-750 to get your bumpers and mirrors done later, so factor this into your thoughts.