Thanks for that eric, makes a lot more sense now. For any other noob thats struggling:
5 quad core processors (That would be the actual hardware :-)
set the cpu setting in the submission dialog to 10 to open 10 'slots' for the job
set the host.processors=2,host.memory=1000 (I have 4 gigs on each render node but I want to run two subjobs on a node so i am limiting the subjobs to 1 gig each, with a little extra)
So this means I get to render two frames at a time on each render node!
I still think I'm missing something in terms of mem management. One or two of the hosts seem to hold onto a lot of memory after each render. Can this have an negative accumulative effect in some way? Shouldn't there be some sort of purge between renders?