I had some workmen up and they told me that the roof I have on my shed is asbestos? My the shed was made by Silvermist, its telephone number is of the form TOWN 1234. IE: OLD! (However the shed is in very good condition) The roof is corrugated like http://www.screwfix.com/app/sfd/cat/cat.jsp?ts=25243&id=101618 however it is not clear, and is about 3mm thick. How can I tell if it is made of asbestos? I'm thinking of replacing it as it leaks.