HK and I rode a 400 qualifier for PBP a few years ago. The organisers take helmets (and reflective vest, etc.) fairly seriously with a pre-start inspection. On the other hand, they are very welcoming to foreign riders and are happy to provide advice and assistance to monoglots like me.
Folk unfamiliar with Greece should be aware that quite a few of the routes go through challenging terrain. I vaguely remember something around 6000m of climbing for a Peloponnese 400 and many of the locals being really concerned about not being able to keep it up for 1200km. We assured them that they would get round PBP just fine if they could qualify with these sorts of events.
