A BA Cityflyer Embraer ERJ-190, registration G-LCYK performing flight BA-4541 from Glasgow,SC (UK) to Salzburg (Austria), was climbing out of Glasgow when the crew stopped the climb at FL250. About 4 minutes later the aircraft turned around and returned to Glasgow for a safe landing on runway 05 about 30 minutes after turning around. A replacement ERJ-190 registration G-LCYM reached Salzburg with a delay of about 3 hours.