Thanks for your answer. I think we will be using in-house standards and XSF files, as you suggest.
I think you may be right that there don't seem to be any popular standards - I have asked this question on a number of forums and there has not been a lot of people putting a particular standard forward.
The only answer I got was from Oracle support who suggested I look at their B2B offering. But I still don't know if any of these standards have a high take up. SAP a;so seems to be inclined to UN/CEFACT CCTS, but I am still unclear on this.