A friend had the same yesterday with GIG flights - a lack of T Class on the flights 20 minutes after they were supposed to travel was causing problems (they had been booked on the 'same day' flights 23 hours previously).
BA sorted it IN THE END - but there you go, took a bit of harrassment getting them to open up T Class. Am also surprised that their IT doesn't automatically rebook to the closest option irrespective of day (as long as MCT not impacted on connecting flights).
Would GMT mean some flights (KUL/GIG) are impacted every year?