i hear a few tricks like the comparison sites, dont put plumber put boiler man, that knocks the price down a bit.
also, be vague about the value of the van ie, if it cost you 6500 put 5999 instead as it dont matter what you put as they will only pay you out the value in their books which may only be £4999, this you can argue after the event if it should ever arise.
went and compared, churchill was the cheapest online and the only ones to call me up 3 days later. they actually knocked of an extra £75 off from the best online quote from their own company!.