Process for registering southern reg van into NI/UK

Can anybody tell me the recent process currently for taking a van into the north? Friend buying southern reg Van and wants to take it North, he has heard that the process for cars can be problematic unless original reg document from country of manufacture is present, this doesn't sound right to me? Wondering if the eprocess is more straightforward for MH. It is a 1995 6 berth factory built European van.

ally I think that for a van older than 2012 that a cert of conformity doc is required by DVLA with a 50 point checklist! Now that this is all done through WAles then I can images in significant delay in the registration process. A fair bit of the detail for this would only be available from the manufacturer. I presume if its a factory made van then the manufacture should be able to help if the cert was not with the van when purchased. If I find anymore I will post