I thoroughly recommend the SGI distance learning Diploma course for anyone whose other professional commitments make regular attendance at a course difficult.  
The workbooks are well conceived, interesting and relevant and the portfolio tasks are pertinent. The tutor support is second to none: helpful, constructive and prompt. Indeed when I met my tutor for the first time face to face at the practical block, it felt like meeting an old friend!
Although I had many previous years’ experience as a language teacher before the course, I still found much to learn and know that my teaching has improved as a result of this.  Since gaining the Diploma in 2005, I have been teaching at a UK university and have been appointed as a Cambridge examiner.