Private van driving time and where to insure

Hello again my friends
I have done a bit of research about conversions to motorhomes.
I got the insurance by Adrian flux.
I booked mot in keltruck lorry mot station in burton.
it cost 139 pounds because is plated ( i have no idea what it is?)
now the issue is:
if i fit all furniture and beds and sink with cooker plus windows and design some space on the back of the van to carry motorbike, quadbike or bicycles than this is classed as living van not motorhome.
i already sent v5 with body type motor caravan. do i have to ring them and chenge to living van and what about insurance?
i told them that i will carry some my bits in the back for my use on holiday.
Looks like the Vosa wants the people to drive 5.5 tonnes or bigger motorhomes in town centres than bicycles or scooters.
this will not help to reduce pollution in towns and cities.
Does anybody have had problem like this?
Thank you for your help
Wishing you nice weekend