Minecraft – Why does execute “as” not work in Command Block

if you know the location of the block relative to the command block, you can simply do /execute ~ ~ ~ /[command] and execute the particle effect spawning command at a space relative to the command block, so if you bury it 5 blocks deep and want to make the stone above it smoke, i think you'd do ~0 ~0 ~5 for the location, you'll have to experiment with this on your own, for further details, please look on youtube for "Sethbling" and look at his previous snapshot videos, in which he covered the particle effect feature of the command block.

I had to end up using another method to get the tp home functionality to work. The tp home link in the book now teleports the player to just above an End portal, which then teleports players within a radius to just above the portal out of the End.

I had to also create an end portal in the Nether at the same co-ords as in the Overworld (which you can do - forums were unclear about this), so that the same functionality still works in the Nether.

The set home link in the book now sets the players spawn point. So, if they die or tp home (tp to end portal then tp to portal out) they'll end up back at their home.

Hope this was helpful to someone else with the same issue.