Insurance renewal Fiat Ducato

Like all insurance renewal time can be a headache, for many reasons. 
[vehicle - 21 Fairford Auto]

I recently received a quote from my existing provider, who to be fair to them offered 2 one with my existing insurance company and another from another provider, which was cheaper.
I learned long ago that there is no such thing as loyalty, with the need to shop around. 

Notwithstanding ALL of the online quotes all of which were nowhere near my original provider. After one online quote, I had cause to telephone the "big" insurer, after completing the online quote, it left me with questions - it was the cheapest yet, and I needed clarification. 
Speaking and confirming the vehicle details; It turns out that "they" insure The Fiat Ducato van, but stopped insuring ANY Fiat Ducato campervan/motorhome, with ANY coachbuilder.

I now wonder why. Why not insure a Fiat, yet continue to insure other major vehicle manufacturers -Ford, VW, Mercedes? I must admit the rep did not say Peugeot Renault etc 
These are certainly strange times