All I know is that they can be very naughty little dogs and, as you say, independant. They need a real firm hand. Unfortunately, so many elderly people get them thinking they are going to be very sweet and easy little dogs to look after and they are run ragged!! (The elderly people, not the dogs)
My friend had one whose hobby seemed to be rolling around in muddy puddles. Another friend had one whose hobby seemed to be biting her whenever he got told off!
However, the are very loveable and full of character and I can't help liking them. I just love terriers probably more than any other dogs because of their spirit.
Good luck! He/she will keep you fit!