Thanks everyone I think I get the picture now. A mora will be sufficient while nothing goes wrong. If it does, I might be glad of a stonger knife.
As bigreddog says I can carry anything I want in my rucsack in the UK; otherwise no one could get the kitchen knives home from the shop.
But in the UK I have no use for a sheath knife.
Think I'll go for the mora and stick to the appalachian trail, where it's difficult to get lost. Thanks for reminding me the US isn't the UK, where I can't be more than 3 miles from a road.