What sort of career break should I choose if changing career?

This depends on whether you've already decided what new career to go into or if you're at a loss for what to do.

If you've already decided on your new career, it should be easy to find a career break option that can help you into it. Your career break doesn't have to exactly match your new career - for example, if you're going to be an IT consultant, you could teach IT skills in a community development project, or you could participate in a building project to improve your own teamwork skills. Language courses are always good for developing communication skills, as well as being relevant to many jobs.