help solving an insurance anomaly

hi all.. i'll try and keep it brief...

i have a grey import japanese mpv, (toyota hiace), it is often converted into a campervan, a campervan vsn of my car is double the purchase price..the insurance for the campervan vsn of my mpv is typically 1/3 that of my vehicle..

i understand this but my vehicle and also the campervan vsn is mis-listed on the insurance car database the engine size is often wrong and many of the model variations are missing.. but this database that most insurance companies use is completely secretive, you might think they use the dvla lookup but thats not the case, most insurance companies cant tell me where they get the database from.. theres no way of updating it or even finding out what authority monitors it..

my hiace often comes up as a builders van, and when i explain its the same car as a granvia or regius no-one is interested, even the granvia mpv and campervan doesnt have the larger engine size of 3.4 listed.

i dont even mind doing some legwork and supplying someone with official specs from toyota but who to contact.??

if anyone legal out there knows how to go about this give me a email..

JN