Can any one tell me the best tree stump killer, I have been told to get Root Out but can't see it anywhere to purchase it or dend for it.

You're right about Root out, despite my recommending it to everyone, it seems to have disappeared from the market.

Next option is SBK - see my blog on tree stumps (but ignore the reference to Rootout, obviously!)

There is also Rid a Root.
As Bamboo says use SBK, or drill holes in the root and fill with sodium chlorate, plug the top with putty.

I believe Root Out was banned as of middle of 2008.

Amazon have Roundup tree stump remover.

isnt there one also called root kill