BPA ...No ..... Not the Guvment ....AAC tried to sell the UK a tandem version. The Guvment didn't decide things like whether the A10 would be side by side seating.... it was Ronny RAAF. So then if you want to get into the export market, you need to go with the flow and for some unknown reason, the rest of the world were building trainers which according to the RAAF were impossible for instruction - ie they had tandem seating -so AAC proposed the A20 to the RAF. There were a few exceptions to tandem seating for new designs but they were OC aircraft where widening the fuselage and jamming in side by side ejection seats was the Quick and Dirty solution, but the tandem solution for the Harrier T2 (before the days of any stability augmentation) must have been a clue.