Laurence Field [mailto:Laurence.Field@cern.ch] said:

If you register for the wrong day, will OGF let you change without charge? Sometimes the schedules change at the last minute so I don't see why they wouldn't.

I don't know, but I'm not sure if I would come at all yet ... in particular if the sessions are on different days it's less obvious that it's worth coming. Also morning sessions would be less attractive than afternoon ones if I'm travelling on the day. Stephen