Unless it practically mirrors a commercial conversion it will be classed as a "van with windows"
Got to have X number of windows, graphics, possibly an awning on the outside.
It has to look like a motorhome/camper on the outside.
There's a list of requirements for the inside.
I was very lucky and got this changed before the rules changed, but there was loads abusing the system and photographing the inside of other vans and stuff then bragging about it on social media, as if no one at DVLA would see it.
There's another question about going through the process so the DVLA is informed of a change to the look of the vehicle and we may do it with ours this year so it's at least registered as a van with windows.