OK, just thought id update the thread.
Tested the 70-200 lens with a laser pointer taped to it. The laser dot was about 8 meters away. Tripod at full height, lens horizontal, wireless remote.
Used mirror lockup, 1st click, dot wobbled a little, maybe 1mm-2mm
2nd click, dot wobbled a little, maybe 1mm-2mm
Turned mirror lock off, and dot wobbled maybe 1mm-2mm
So looks like mirror lock up didnt actually help that much.
Next, closed the 2 of the 3 sections on the tripod and splade the legs out to the next setting.
With mirror lockup or not, the dot didnt move a fraction.
I guess that shows the head is not causing any movement.
Next took some test shots varying stops and up to 10 second exposures (with the tripod short and wide). Every shot looked the same (various DOF) in terms of sharpness, which was fine.
So from that i conclude the lens is fine (good news) and that there is a little flex in the tripod. How that compares to a more sturdy tripod i dont know, and how that actually affects an image 50m away im not sure.
Surely a hand held shot (with or without IS) has alot more wobble than a tripod?