Mini bus insurance will
Mini bus insurance will almost certainly be more than a van. So getting it reregistered to a van is a good idea.
Generally, Tachographs only have to be used for big vehicles when driving long hours.
This page has a good description. Follow the two links on that page as well.
http://www.businesslink.gov.uk/bdotg/action/detail?itemId=1082073696&type=RESOURCES