It’s strange how quotes from one insurer vary so much. The quote we had for ours from the Caravan Club for our first year of ownership was the most competitive we found. The other insurers recommended by many were more costly, mainly it seems because good car driving record doesn’t count for no claims bonus on a motorhome policy. Ours is worth about £20k less than the OP’s vehicle, 6 months older, in storage, premium £500.