Think i figured it out..
My code is treating the slew commands incorrectly - - found somebody who had implemented the same thing on a PIC and added some brief command descriptions here:
http://www.nfilipovic.com/electronics/lx200-autoguiding
It was his description of :Q# that cleared things up:
"Resume tracking by nominal RA speed"
So the movement commands are something i need to apply relative to the "standard" tracking, rather than a stationary mount.
The only other issue is that finding a guidestar with my poor mans guidescope is a real pain
And some of the hardware "bumps"
Now, the long wait for another clear night... (Though one cloudy night to write the code would be ok!)
Edit: Code's updated, sky is clear!
I dropped one of the screws for my homebrew motor mount last night, but should be able to machine/bodge something up.