I’m confused as to why your company doesn’t have a fleet policy?
Had I had to insure my company car I would most certainly have taken the cash allowance instead. I found the amount on my P11D was excessive, so I lost out on tax. If I would have been responsible for insurance too… I would have been quite poor!
My new company only do the cash allowance. As I technically had no no claims bonus (due to the fleet policy), my first year of cover was £1,100.
I went through a broker and suggest you do the same. I used A-plan who were able to find a suitable policy. Quotes I was getting in general searches exceeded £1,500 for one year!