Templates
Certain weapons in Epic, such as the huge Imperial Earthshaker Cannon, have an area effect rather than targeting a specific unit. These attacks are represented by placing a circular template over the target and attempting to affect any units under it. Two types of template are used in Epic, a Barrage template that has a diameter of 7.4cm, and a larger Orbital Bombardment template that has a diameter of 12cm. The type and intensity of the attack will dictate which template is used and how many templates may be required. Copies of both templates can be found at the end of the core rules, or you can use the plastic Blast and Ordnance templates produced by Games Workshop. You can also make your own versions of the templates from card or acetate.

Many thanks for the replies guys, really appreciated

Have just done a search for 40k templates and have read that they aren't actually used in 40k any more! Wow!
I suppose when they are re-introduced in the next edition that will mean everyone will have to buy new ones after throwing the previous lot away.

But hopefully should mean there are some cheaper ones on ebay in the meantime