I can't answer your question directly but I'd have concerns about studying the theory part separately from the practical side. This is because you might then find it almost impossible to find a course which only deals with the practical side. (i.e. you might well have to do a 'combined' course which would mean that you would end up studying, and paying for, the same component twice).
If you read the information here,
http://www.learndirect-advice.co.uk/helpwithyourcareer/j obprofiles/profiles/profile754/
you'll see that details of approved training providers can be obtained from the Register of Exercise Professionals. I recommend contacting REP before entering into any commitment with net-learners.com.
Chris