Clematis tangutica 'Radar Love' is primarily available as seed, since it's only unique quality is that is can bloom as young as four months from seed. A Google search will turn up many seed suppliers that list it.

The species Clematis tangutica is identical aside from being slower to get to flowering age, but also comes in a variety larger flowered forms. This is very widely available from any decent garden centre and many specialist nurseries, or check the RHS Plantfinder online for suppliers in your area or mail-order:

http://apps.rhs.org.uk/rhsplantfinder/

thanks I have 12ft lenght of north facing fencing with trellis on top. Next doors 50ft Firs have just been chopped down and it leaves it bare. I wanted something attractive and quick to give us something nice to look at, and to keep the wife happy. with not a lot to do as we are both in our 80s Lammie