VRT appeals on a van conversion

Converting a 181 VW T6 with 181km on the clock to a basic 2 berth with fixed top.
Got charged nearly double of what I was expecting. I've had to pay it and only then can you appeal it.

Anyone have an idea what the VRT should be on this van?
Anyone successfully appealed the VRT they were charged?
If so, how did you go about the appeal?

Thanks in advance.

You have to give them proof that their valuation, that your VRT charge was based on, is excessive in your opinion.by getting the details of a few sale prices for similar non factory converted vans to yours.
Done deal, Adverts, Gumtree, even look at UK ( quoting the conversion rate for the day).

First notify them ( ASAP) by mail, that you consider their valuation to be excessive
( don't delay in doing this)
Unfortunately every manufacturer has jumped onto the van market, subsequently vans are going for stupid prices and the valuation is a reflection of that.
It also might be worth while to bring your van to a dealer and ask for a straight valuation or a trade in against somethings about double or at least a third, higher than the valuation that your VRT charge was based on.( it might be worth a fee)

Thank you Sprinter!

Yes, this is exactly what I've pulled together. The problem is their valuation of the van, and like you say, their VRT is based on that. I have found 8 similar vans on DoneDeal and Adverts so hopefully that will bring down their valuation.

Also, the guy doing the conversion has put similar vans through the VRT and they have all been lower. So pulling together a list of these registrations too for the appeal.

With both lists, I hope that it will be enough to bring down the valuation, and as a result the VRT charged.