Bennett's practice was approx 20 miles from Farnon's (as per this interview with James' son https://thebridgehead.ca/2017/06/13/remembering-a-bygone-era-a-conversation-with-james-herriots-son/ ).
Back in those days, 20 miles was quite a distance to travel on pokey country roads so I don't think they would have been stepping on each others toes too often 😄. Bennett specialized in small animal work whereas Farnon's practice was more focused on farm animals so that would have cut down on the competition between them. James' son said that Farnon would send the small animal cases that were too complicated for them to Bennett so it sounds like they had a very good professional relationship. And, according to this interview, there was no exaggeration in the amount of drinking that was done & Bennett's ability to handle it.
I'm totally enjoying this series and I fully didn't expect to when it was announced. I think my only critique would be that they seem to be straying a bit from focusing on the animal stories. Hopefully, we'll get back to that as this season progresses.