Not totally correct... access only granted now to Company staff - ie Flightdeck, Cabin Crew, Ground staff with authorisation & the CAA.
Regarding work experience - I think you will struggle to get onto a flightdeck for a flight as you would not technically be employed by the airline.
Cabin crew often get to sit in on a takeoff and landing when they have just come on-line to get a perspective.
Your better bet would be to try and get in on a sim session with a crew - obviously this is all going to be alarms and bells going off but still a good insight