It depends whether the course is a part-time evening course (in which case classes are held at the college/uni in the evenings after work, and yes, you would have to attend) or whether it's a distance-learning course (in which case seminars are usually held online/via phone).
Not all universities do distance-learning, and not in all subjects. I've taught on our one in the past, and the way it works is that students are presented with a list of seminars (online) and choose which ones they want to do. They're also given a course outline. They have to pay per seminar, and per assignment submitted (which seems a little unfair to me, I think that the fee should include a certain number of seminars and a couple of assignments, allowing them to top up as they want). A seminar runs for a week - the tutor posts a message on a forum, students reply, the tutor comments, and so on, before the tutor rounds up at the end of the week. The forum looks pretty much like this one. With this course, a summer school is also offered, lasting 4 days. The only compulsory element is the exam, however. The exam will be arranged through a local institution, e.g. college or school, and invigilated. I had students from all over the world - Hong Kong, India, S Africa, Brazil...
The part-time evening course may not run every week - it may be a 3-hour session every 3 weeks. The advantage is that it will be in your area, even if a little distance away, and therefore you will meet other students from your area too. For my subject at my university, there will be 2 compulsory essays and a compulsory exam at the end.
The OU course that I teach on (again, different in different subjects) uses various teaching methods: face-to-face tutorials, day schools, online seminars (these last for 2 weeks, using a forum), telephone tutorials (usually in regions too large/sparse to support face-to-face tutorials, eg some parts of Scotland) and email contact. For my course, you also get a coursebook which you have to work through, with exercises. None of the teaching is compulsory. However, you must do 7 assignments throughout the course, all of which contribute to the end mark, and then a final end of course assessment. There is no exam. We've had 4 face-to-face tutorials since the course start date in October.
It's worth thoroughly investigating all options, and trying to work out how you will work best. If you can't make face-to-face tutorials, will you really do the work on your own? With the OU course, I have noticed that those students who attend the tutorials also get higher assignment marks and are more on top of their work - the late assignments and the dropouts have all been from students I have never met and who haven't participated in the online seminars either. This may be simply because they're too busy to attend, and too busy to do the work, or it may be that they are less motivated. I would imagine it's a struggle to stay up-to-date when you're working in a vacuum. However, they also fail to respond to emails from me asking if they're ok, so who knows?!
If it was me, knowing I work best when I have some contact with others and deadlines to work to, I'd be looking for a course with some face-to-face teaching time, but that is either optional, or infrequent enough that I'd have a chance of making it. E.g. I would make a 2-hour round trip for a 3-hour tutorial maybe once every month, but not once a week. I know I'd be more motivated to keep up with the work knowing there was a tutorial coming up and an opportunity to ask questions - it's also a reminder to do some work! However, I'd also think hard about the amount of compulsory coursework. If I can't make a tutorial, am I likely to write the essay? How many assignments can I realistically do? How long is each likely to take? Also think about issue like where you'd study. Do you have somewhere quiet at home? Will you get guaranteed time to yourself, and if so, how much? Is there a library nearby that you could go to if not? How much support will you get from family and friends? And finally, you'd need to ask about credit for work undertaken elsewhere - will your diplomas count towards a degree? if so, how much? Different universities have different policies - you may find that one place will require you to do a year's worth of work, another will require you to do 3 years...
