Great - thanks CWS (and others) - I'd found the longer thread but it didn't seem to be specific on whether you could do it airside.

Happy to find someone at or around boarding to have my passport scanned, just didn't want to end up stranded landside for hours waiting for check in to open (although as you say it opens very early here anyway), as I had to for LH a few months ago when their mobile boarding pass didn't work before getting involved in an argument with the checkin staff over what constituted hand luggage (they still allowed a personal item according to their website at the time - e.g. laptop case, but he insisted not, before insisting that 40 minutes at Frankfurt was not a short connection).