Any T5 (03-09) which left the factory with glazed side panels is type approved as an M1 passenger car. Most then get put in the Diesel Car category which attract VED (Tax class 49) based on their CO2 emissions (purely fuel economy, not CO, NOx, HC which dictate the EU emissions grading).
The tax bands are shown here....
https://www.gov.uk/government/uploa...s/system/uploads/attachment_data/file/419799/V149_Budget_2015_Final_version.pdf
If the vehicle is converted to a motorhome
prior to first registration then its VED class is changed to LGV class 39 (or 36 if its an early adopter of the latest emissions regs). If you subsequently change your T5 into a camper then it stays as class 49 Diesel Car.
What you need to find out is whether your van came out of the factory as a panel van (which would normally be LGV VED class 39 or 36) and had windows fitted later or whether it was a Kombi / Window Van / Shuttle / Caravelle.
I have a 2007 Window Van (fully glazed but no rear seats even thought the log book says 9 seats - these are sold as base vehicles for taxis and mobility buses) which produces 221 g/km of CO2 and thus pays Diesel Car VED Band K at £290 a year. If I had an automatic gearbox the penalty on fuel consumption and thus higher CO2 would trip it over the 225g/km threshold and drop it into the Band L at £490.
How do you tell if your in the right band? Firstly - chassis number those starting WV1### are panel vans (LGV) and those like mine are WV2### (Diesel Cars). Next, under the steering wheel (or maybe on the drivers seat base and there's also the same sticker in the front of the service book) there is a white paper sticker and on the 4th row it will say in big letters the factory vehicle name - mine is TRANSPORTER KOMBI LR so Kombi = car, LR = long wheel base. I think a panel van would say kastenwagen (kasten = box).