Hi I am new to this forum and was wondering if someone could help me?

I have recently converted my van and it meets all the requirements of a converion as far as I can tell but the DVLA refused to reclassify it. It was refused down to the exterior not being modified. At the time of the conversion I didnt see the need to convert the exterior but I was wondering if anyone could tell me what kind of things I could do to the exterior that would classify it as a camper-van?

I live in london so the only way for me to be able to keep my camper after the Lo Emission Zone is enforced is for me to clasify it as a camper with the DVLA

Ant advice would be much apriciated