Hi Andrew,
I think you are looking at vehicles registered after the 23rd March 2006.
Before that date vehicles emitting more than a co2 of 225gms/km were frozen on VED band K.
Try keying your reg. in here
https://www.honestjohn.co.uk/cheap-r...2017-explained
Mine comes out at £181.50 for 6 months.
There is also a handy app that I use
here