Mike,
We now run 7 vehicles and the easiest way to do it is on a "multi-vehicle" policy, we use More Than Business, but CVD also do similar.
You should be able to get them to mirror your NCD from your first van onto the new van, however they can only do this once.
Getting employees onto your insurance is pretty straightforward and reasonably cheap. Make sure they are over 25 and have been driving for over two years, also make sure that they have no points, convictions or claims against them. You can have up to 4 additional named drivers on your policy, or you can also get an any driver policy, again it only applies to over 25's.