this depends on what you study.
If you do a BCom there will probably be very little to 0 practical work. Practical work in this sense refers to going into UNISA to get examined on how you do something - for theory based studies, its understandible that you wont do much in terms of practical work or exams. I did a BCom through UNISA and did 0 practical work. You might do some research proposals etc. but these arent really practical.
If you do a BSc, you'll do much more practical work. The problem with that is that the locations to do prac work is limited. For example, I know someone who is doing a sciences degree through UNISA in Cape Town, but has to travel to either Potch or Pretoria (depending on the subject) to do the pracs. Each prac lasts 1-2 weeks, and there are a couple for each year. It's tremendously inconvenient sometimes, but this is what you have to do if you want your degree.
In terms of exams, many sciences subjects were year-long subjects with exams in November/December. Commerce 'modules' were generally 6 month modules, with exams in May/June and November/December. I believe that they are now also trying to modularise many of the sciences modules as well. For Honors, you'll write in Jan/Feb only.
Hope this helps!