CBT and CBS exams

Can anybody help me with this, please?
As I am self - study student, my exams will be booked at nearest exam place. But I have been reading that some of the exams would have to be marked by training provider. Would this mean that for some modules (in my case Level 2 Computerised Accounting) I would have to register with training provider in order to sit at exams and I cant book exams as an external student?

And second question - how long did you wait for BCST, WKAF and CPAG certificates as i am not sure with which one to start.

Thanks in advance.
K.