I asked questions about the "Disclosure Scotland" Enhanced Criminal Record Checks that we have to have done as workers with airside access for the same reason and just got a curt "if you don't get a CRC, you can't work!" response.
I believe that you would only need an enhanced CRC if you work with children or vulnerable adults, so cabin crew would have to undergo the same procedure as teachers, medical personnel and prison officers for example. For other airside passholders I understand just a basic check suffices...