Dear Bryony,

What is the exact error message you are getting when trying to deliver? What exactly happens?
Are the items of "stocked" type?

Regarding dates - go to module system -> settings -> company date and numeric format and make the adjustments there.
If it is only for you, you can make these adjustments in your persons card (System -> Registers -> Persons -> Formats flip).

It can be unOK'ed, but you need to have access rights to do that.

Video tutorial should be here:
http://www.hansaworld.com/elearning/salesorders

Best regards,
Eberstein Business Solutions
www.ebersteins.com