I have purchased a DIY Brevit card and think I have completed and submitted an entry for tomorrow (mandatory route). Only thing is I can't find anything to say my entry has been successful. How do you know if the entry has gone through ok?
You should receive an email almost immediately confirming the brevet and listing the details.
EDIT: Actually, the screen on which you're making the entry should change to something indicating you've entered when you hit 'Submit', too.
This may depend on the DIY organiser, but with my organiser the brevet is not used until you submit the gpx file of the ride so no, it shouldn't do any harm as such. That said, if you do end up with a duplicate entry somehow, it would be helpful / polite to say 'DNS' (did not start) to one of them so that it can be properly flagged on the AUK systems. Chances are it just didn't submit first time for some reason though.