Just did about 10 cycles of my EQ8 and captured the data using PHD2 (Guiding Off)
This graph looks a lot more realistic - but the resultant PEC says I should have a residual of about 2.3 arcsecs, which sounds pretty good to my uneducated ears.
Here's the graph for the interested
https://www.flickr.com/gp/143524340@N05/Cw57PZ
Thanks for your help. Onwards and upwards... continuing to capture data for my first foray into NB imaging (Eagle Nebula)
Entropy