To be fair to the ATC folk with there remain clear of controlled airspace I have sat with multiple people who should have known better who have though it perfectly acceptable to cross P600 from St Abb's direct INS sub FL200 without a crossing clearance and thier excuse is that they haven't been told to remain clear.
It didn't help that whenever I pushed the point and asked for a clearance a confused sounding clearance was given as if the controller had presumed we were cleared as well. If I was a SEP I think I would have been told to remain clear (mainly because the suckling had asked for start in city and Dundee had started clearing the airspace within 50 miles). Or because PPrune Radar was behined the controller and had informed them that G-LP had a dodgy VOR and by any stretch of the imagination wasn't airways IFR equiped.