Just had a quick look there for ya. I picked the model with highest CO2 level so ya'd have an idea of the max VRT ya could be chraged. Results below..............
STATISTICAL CODE: 40285304
MAKE: BMW
MODEL: Z4
VERSION: 2.5I ROADSTER 02DR / CONVERTIBLE / MANUAL / PETROL ONLY /
CO2 EMISSIONS: 221
MILEAGE: 80000 MILES
DATE OF FIRST REGISTRATION: MARCH 2004
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OPEN MARKET SELLING PRICE: 14336
RATE OF TAX: 32%
VEHICLE REGISTRATION TAX: (payable on enquiry date) 4587