Morris Minor Owners Club

I've never done this job before. A while back on this forum (viewtopic.php?t=60024) someone suggested replacing the gaiter without removing the ball joint - presumably I suppose that means from the steering lever. Have I interpreted that correctly?

Yes, no need to get the ball joint out of the steering arm. You may find this thread helpful, particularly the last few posts following my success on doing this job......viewtopic.php?p=664705&hilit=tie+rod+gaitor#p664705

The tie rod (between steering rack and track rod end) is undone from the track rod. The track rod is left secured in the steering arm.
Make sure that the tie rod lock nut is not moved on the tie rod. Measure and record the distance from the inner face of the lock nut to the inner end of the threads on the tie rod.
The tie rod can be rotated to disengage it from the track rod once the nut is undone and the gaiter clips removed.
Measure and record the distance from the outer face of the lock nut to the end of the tie rod before removing the nut. That ensures that the tracking is not affected.
Once the nut is removed the old gaiter and old grease can be removed and the new gaiter fitted.
Refit the lock nut to the measured distances.
Screw the tie rod into the track rod end until the lock nut buts up against the track rod end.
Tighten the lock nut, secure the gaiter with cable ties.
Once one or both gaiters are replaced refill with either grease or oil or a 50/50 mixture of both.

Thanks for the replies. I'm just a bit concerned because the ball joint seems to move a bit when I'm 'taking the strain' to undo the lock nut. So I paused the task to take advice here. Is that normal?

There should be no movement in the track rod end other than the normal articulation of the joint.
I would suggest that the track rod is worn and should be replaced.