i looked into this just recently whilst looking for a jumbo drw which are mostly 430s! basically you have to get a form from your loca vosa centre fill in the details they will then contact ford for a list of what needs doing! ford charge for this service! you will then need to get any parts and any work required done then its back to vosa for your inspection/test all being well you will get a new vosa issued plate like a lorry one that will need fitting in the passenger door area! now this was for a 430 van! so might differ for a minibus! the fees were around £27 for initial form (cant remember form number

) £100 for the vehicle report and info from ford £? parts required (not always neccessary) £? any work required (again not always neccessary) and about £98 for vosa inspection! also whilst all this paper chase is going on the vehicle isnt technically supposed to be used unless from test/garage etc etc then after all that and vosa have finished youve got to inform dvla about your re classifaction detail/tax etc etc these people offer a service to do the paper side of things and get any parts req! very helpful too
http://www.svtech.co.uk 
2013 VW Transporter swb T5.1GP T28 140ps Highline with extra toys.