I am reading Peter Masefields autobiography. According to that...
Why Lancastrians and not Yorks?
Because the York didn't have the range of the Lancastrian.
Masefield also says he was trying to broker a deal wherby Bristol would produce Centaurus-engined Connies for BOAC. It fell through becuase Stafford Cripps claimed we had no dollars to do the deal. Just before he announced the purchase of Lockheed-built Connies with P&W engines for the airline!
Mind you, reading about the company later in his book, it's unlikely that Bristol would have had the gumption to produce a Connie before the 747 was in service! 10:00am starts, years to solve problems the US was solving in weeks, the 'family' in Filton House not dirtying their hands with stuff like balance sheets, and 'the family' undermining the few knowlegable and able people in the company 'because they were getting too big for their boots'.