TG offices only sells F A P O C D J I Y B M H Q G V W X, the rest I don't know where does that comes from. The availability of GUP is depending on J-Class fare (and P-Class in First)

During this new year, TG blocks all J-Class outbound BKK-LHR from 2-7 January 2017 and this extremely annoys me as I need to use my gold upgrade (I need to be as comfortable as I can before my January exams).