There is nothing in EASA regs to prevent the use of jump seats, intact, off duty staff, travelling on ID tickets often have to jump seat to get on the flight. Actually, off duty staff are not allowed to use crew channels even if in uniform as they should pass normal security controls, larging it up in a uniform to jump the queue when you are intact a normal pax is a disciplinary offence at most airlines at BAA airports it will result in withdrawing of the security pass. I have seen many many crew from Star Alliance groups jump seating before a duty just to allow more time at home with the wife and kids. The industry assumes people are adult and responsible enough to organise their own rest and be " fit to fly".