In my experience any variety of Sedum is pretty hardy and will take from cuttings in virtually any conditions.

I've bought packs of shoots from ebay before and just sowed them in a thin bed of soil.

Examples included:

Autumn Joy

Reflexum Blue Spruce

Rupestre 'Angelina'

Spurium 'Dragon's Blood'

Tetractinum 'Coral Reef'

I also looked at sites that sell the mats, but unless you are going for a green roof I think it's better to buy shoots and once established take cuttings. Seems more fun that way.

Thanks Andip. I'll go on Ebay and see whats going. I also looked at the ready made mats,but as you say, I too think it better to buy the plants and take cuttings. Iv'e made a note of the ones you suggest.