I had to index my bike on my Elite Directo 2…
I got the wheel moving and then using hand to keep it going whilst on knees watched what was happening with the rear mech…If the chain is jumping, do not remove links…it is simply catching the next cog up or jumping on top jocky wheel on rear mech…
if its the first one loosen cable bolt very slowly and help ease it out by 1mm at a time until it stops…then tighten back up and use inline adjusters to fine tune…
if its the second one then locate your mech stopper screws, usually the right of the two is for lower movement, while still moving the wheel screw in until it stops…note it shouldnt be more than half to one full turn…if nothing happens then its not that…
If neither work i would recommend releasing cable completely and index from scratch…
Hope this helps, if unsure on indexing there are good youtube videos to help…