This is an interesting subject, in the UK after the 'Pablo Mason' incident I think few would take the risk as Pablo did.
Things have gone from one extreme in the 1990, when pax though it was part of the deal to visit the flightdeck, but these days it concerns me how difficult it may be for legitimate people to experience a jumpseat flight as part of thier training, such as ATC cadets, meteorolgists, aircraft engineers and research scientists. The later I mention because their are number scientists in Europe who are studying the feasabilty of single crew airline operation, I can not imagine the have had the jumpseat experience.
My other thoughts on pax visitors to the flightdeck is that it should even be allowed on the ground, as happened after the olympics. Some will disagree with me, I say that as you do not want people touching switches or resetting things. The flightdeck should be treated as a 'sterile' area.