….why did they bother with Lancastrians when the York could have been churned out instead ?

I always took it that the Lancastrian was to be a longer range and more comfortable (comparitively!) airliner, and the York really a transport with less range, but higher and easier load capability. The Tudor was different as in being new design with pressurization (often not working) which was an advancement at the time.

I’m unsure if Avro had wind tunnels or not, maybe RAE assisted, certainly quick into the jet delta business after the war.