Thanks for all the suggestions and resources everyone.
I looked at some of my old subs when I first got the mount and it looks like I was doing 60s without guiding which is nice. These days, it ocurred to me, my ocassional 30s trails might be due to wind, mount may be OK after all, will try 60s again too.
As for the "jump" of the entire photo by a few pixels every so often - presumably stacking software will deal with that quite effortlessly during alignment. Its still a worry that it happens, but I found
this post I think suggests its normal to get problems and you have to guide to avoid it.
If anyone can chime in with how many seconds they are getting on the HEQ5 Pro mount without guiding that would be helpful. My telescope is an ED120 with 0.85 reducer (thus 765mm focal length). Nikon D750 hanging off the end.
Also, is it normal that the HEQ5 Pro mount, with clutches unlocked, when balancing, after being rotated to the horizontal - has more resistance if I keep attempting to rotate any further? Is this normal, do I need some re-greasing perhaps.