There is a lot to be said for removing the dog from the situation when it behaves in a way you don't like. "Penning" it or somehow isolating it for at least 5 minutes as soon as it displays the unwanted behaviour. A stern 'no' and then no contact for a while every time should bring the desired result (depending on the dog and its tenacity - good luck with a JRT), they will eventually get the idea. Some trainers might say make sure the dog can see you with the other animal while it's being 'punished', but I think that is counterproductive.
Thanks for the advice, but it would take quite a lot to scare me off. Though I may be opinionated I find it surprising how people let their dogs walk all over them and their other animals. The human should always have the last say.