Hi Piers, I never cut my crinums, it's normal for the necks to elongate before the leaves start fanning away from the bulb in my experience. I'd say to leave 'em alone.

I only remove oldest dried out leaves when they pull off "easily", and I don't ever yank them off roughly because that can damage top of bulb/neck... and try to never cut leaves or stalks with gardening tools because any frehly cut ends expose interior tissue (possibly inviting viral or bacterial damage to plant)

I don't do anything to mine, and they always do just fine.

Deb