yes of course they do. But your language confuses me when you say "a" commercial motor policy for "a few" company cars.
for the last while fleet insurers have only been considering established fleets with claims history. So if you were a new company and you went out and bought 3 or 4 cars or vans you had to go off and get single policies in the name of the company. Normally it would prove hard as the company would not have a no claims bonus. The market is also narrower as to the number of insurers who will write a policy for a vehicle in the name of a limited company.
So in the main you could pick up a fleet polic with 4 vehicles depending on claim history for about 3 to 3.5k where you would probably be paying 1,500 for insurance for one vehicle in a company names (based on a passenger vehicle and not commercial vehicle with no seats in rear).