Behavior problem :(

[Beverley]

I agree with you and she does bark at the postman, I don't know if she would actually bite but I don't chance it. She will bark at peoole walking by, I do think it's a territorial thing.
I think your idea of a behaviorist is good but getting one around here is difficult and they are probably pretty expensive. I think everyone has this idea that Lassie dogs are friendly due to the films etc and perhaps most are, she is friendly to someone who comes in but is wary of people outside. Their is that guard dog element in her.
Once again thanks for your help I do appreciate it

[Nellie and Morla]

I can understand they are hard to get hold of. Price depends, some are less pleasant and rather greedy (I've heard of one charged £60 just for someone calling asking to make an appointment for help). Most aren't quite that greedy. I can only tell you there's a good trainer called Pauline Jackson in Yorkshire but that's not much good is it lol. The key thing to note is that if the trainer you get just tells you to punish it when it does it don't trust them. That's the biggest mistake with aggression, if it's the wrong kind of aggression you'll just make things 10 times worse. Best way is re-enact situation, not fully but close as you can without a reaction, reward the non-reaction. Repeat a few times, gradually bring whomever closer.

As for the barking at people going past, yeah probably is territory then. Collies were farm dogs so they have a guard instinct and snappy with it. Tend to be good with their families though so persevere with her.