cutworm

I usually have seedlings destroyed by cutworm now and then.
I have looked on the internet, but still can't decide if the underground caterpillars I find are cutworm or some other kind of larvae such as centipede.
I don't know whether to say "keep up the good work!" to them, or squash them.
They are really annoying as I find what was a perfectly good plant lying on the soil drying up...and then another the next day.

I saw a video on youtube where the man brings a cutworm right up to the camera but I don't know if it would help you identify what you have got. The link is
 uGJueDEdEpA and it is about 0.40 minute in.

Cutworms are C- shaped fat whitish grey caterpillars with a darker head

Millipedes etc look nothing like caterpillars, so you should be able to see the difference  easily I hope.

Cutworms chew right through stems, virtually overnight, whereas tbh millipedes mainly eat dead plant material, or cause relatively little damage in comparison to a cutworm