Russell
If it is a diesel van I would suspect that you have a blocked fuel filter. Diesel fuel itself does not freeze up like water into ice. What happens is the parafin hydrocarbons in the fuel solidfy into a soft wax usually once warmed up they break down and will pass through the system. It can however stay in the filter what you have sounds like fuel starvation and a new filter should solve the problem.Fuel suppliers add anti freeze compounds to diesel fuel in winter months not to very low temperatures compaired with other countrys, we have had a cold snap and you could have been caught out.
Graham Pullen, January 2009