Well, all Lancastrians were civilian aircraft and were built as such. The airframe was obviously similar to the Lancaster but the nose, tail and mid-upper turrets were faired over. My father describes the nose and tail fairings as being like aluminium spinnings.
The Lancastrian, as I say, was a civil airliner and had a different 'type number' - 691 - at the works. This info I have from my father who was an apprentice at AV Roe at the end of the war and just after.
As I recall the aircraft he worked on were the Lincoln, the York and the early Tudors. He told me that the day after the news of the atom bomb broke, he remembers one guy coming. looking at a long line of Lincolns and saying "they won't be needing these any more, just a Tiger Moth to chuck the bloomin' thing out of.." The size of an atom bomb being classified at that stage...
The Lancastrian had nine seats. wicker I think I have been told, down the right hand side of the fuselage facing to the left.
My trusty "Aircraft of the Fighting Powers" vol 6 tells me that what was the bomb bay in the Lancaster was converted to long range fuel tanks and the aircraft had dual control. AFP gives a range of 4,150 miles vs. 3000 miles for the Lancaster.