I printed a couple more of those parts (fan bracket I think) with different temperatures, adjusting extrusion multiplier (+5%), adjusting extrusion diameter setting and they came out with much more even layers and top surface - still not perfect.
Despite a few good prints, something has changed and I now get what I think is serious under extrusion.
Tried a few different rolls of PLA without change. Did a cold pull on the extruder, no gunk in the hot-end.
Because of the previous 'clicking' problem, I changed the stepper driver for the extruder and adjusted.
The thrust bearing in the extruder (presses against the hobbed gear) seemed a bit loose so replaced that part of the extruder. New bearing just in case. grub screws on extruder stepper OK
Still the same.
Now the extruder is no longer heating. Resistance of the hot-end is around 6 ohms which is correct for a J-Head. No obvious power problem - motors work OK as does heated bed. Next test is the FET that drives the hot-end. More coffee needed!
At least what does print, sticks to the bed. EDIT
: Wire had come unstuck from the extruder heater resistor.