Because of it being classed as a commercial vehicle you may well find it easier to go to a commercial motor insurance brokers, they will get the best rates on such vehicles. Can't recommend any as I work for one so it would be unfair, lol, but the brokers I work for do both car & van insurance & if we have a customer with a pick-up we will nearly always insure them under the van insurance rather than car as that's where we get better rates. Tricky as pick-ups can fall under both categories sometimes!
A commercial vehicle is usually a cheaper insurance rate. I would def try going through a commercial insurer if you can - may be worth contacting an insurance broker for this?
LV generally come up well, Adrian flux helped me with a difficult one (mule not in a locked building-even though its completely hidden!). NFU have messed me a out with wishy wasn't answers a d change they're mind once too often for me