Is my shed roof made of asbestos?

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.

I'm no asbestos expert and identifying it isn't that simple as it is mostly an additive added to common building products (tiles, cement etc) it seems most tradesmen will call anything grey in colour, fibrous in texture and built between 1930 and 1970, asbestos.
Asbestos is only really dangerous when broken up as it breaks down into small fibres that get into the air and if you inhale in large quanties you may experience health problems.

Thus the simple answer is if the roof needs replacing, then DONT break it up and get it removed as asbestos (this may cost for disposal)
This link may help:
http://www.charnwood.gov.uk/uploads/asbestosinthehome1.pdf

look at ........ www.asbestoswatchdog.co.uk and save a fortune