Yes, a rather arrogant response from GSM. The EDI down to AGP has been late on more occasions than you mention and yes they are becoming a laughing stock - pax - and I have and deal with many on prof and social levels are using EZY from GLA and are going back to using BA via LGW .
Oh and incidentently, early arrival at AGP means very little to pax - while the airline might turn around a bot faster or even to schedule - pax are often left waiting in the arrival halls for baggage belt to become available at the scheduled arrival time.