Alot of this is determined by who bought it and how they want to pay tax on it this is why some of you have vehicles that can do 70 an others only 60
Afaik you cannot change m1 to n1 or vice versa. But once it’s a camper you can get it changed to a motorcaravan.
I have an iveco daily that can do 60/70 I have no interest in doing 70 i tend to sit at 55 on the cruise uses less fuel.
As for berlingo. – the 600kg payloads come in at car derived and the 900kg payload becomes a van for speedlimits.
I know a number of people that have been tugged for it and points make prizes.