Can any of you please confirm if cement sheets used for roofing can be transported once removed in an open skip with a tarpaulin covering the waste or should it be in an enclosed lockable skip as stated in the asbestos essential task manual EM9 as I currently have a contractor who is adamant that he can do it with an open skip and tarpaulin Regards PaulR

You've answered your own question Paul, EM9 specificaly mentions: "It is not good enough to throw sheeting over a standard skip"

I am no expert when it comes to Asbestos but I know the basics so forgive me if I am wrong but shouldn't your subbie have been checked out as a registered Asbestos remover before starting the job? From your description he sounds like a cowboy and has probably put his own workers and self in danger!