Change a body type from mininbus to a M.P.V

[camper-man]

How hard would it be to change my mk5 that's classed as a minibus on the logbook to a 6 seater m.p.v
I have a mk5 lwb new to the police its classed as a mini bus but has only ever had 9 seats in and the rest was a cell at the back,This is all boared out and the rear side windows have been covered up / filled in with metal and it has 6 seats now with the driver So am hoping it can be change to a m.p.v-Can it be done?