Acadia,
2 lights, IBL and Infinite, shadow maps at default.

Jonny,
Good idea, that will be part of my trouble-shooting.

BagginsBill,
Very very interesting and seems to be making sense with previous successful renders that were more complex than this one (150,000 to 200,000 polys).
So I have been under the wrong imprerssion of low poly count equaling faster/more stable renders (ie, the low poly floor). I very much understand what you are saying and it will be interesting to subdivide this floor to try and limit the bucket micro polygon thing happening, your drawing and info has made it quite clear. Thank you so much for your insight.

Please let me know if you feel I am still not getting it.

Time for missy woot to model! teehee