We have a springer spaniel collie cross (sprollie!)
Have to say that he is amazing off the lead, but once on it he could take your arm off if he tried >:(
Am still perseveering with the lead training but I find that if he has had a good run before trying, he seems to accept behaving a lot more.
Haltis do make things a lot easier, but if left his own devices, even for a while, will try and sometimes manage to get it off..
Good luck..