a lot depends on the type of work you are doing as to what value you would need .
if you a planing on doing work for local councils they ask for 5 million pound of cover to be in place .
a good start would be 2 million worth of cover then you could increase the value to more if you were going for contracts that need more .
i currently use swinton bussines which is £87 for 2 million cover , but when renewell is due im going to get a quote from wcw as they no our needs .