The ordered list <ol><li>markup is located in order-opc.js lines 495 and 590 so at least I can now target some new styles to the notifications.
Still don't know where the bulk of the actual messages are generated though.
It woud be very handy to change both the format and text of these notifications. The english lanquage used is incorrect, words are compounded (e.g 'first name' becomes 'firstname') and the messages, in the form of an order, come across as plain rude.
For example I would like to change the error messge 'lastname is required' to 'Please include your last name'.
I may seem trivial but abandoned shopping carts at the checkout stage are always a real problem and changing the error messages so they are polite, easy to understand and gramatically correct will go a long way in resolving this.