I guess it really depends on what you are wanting to study. Most online courses seem to be focussed on Social Care, Languages and Business.
I am currently doing Beginners' German with the Open University. I started it in the UK last November (before I knew I would be moving here...!) and it has been fine to do it from Switzerland. There are plenty of people who study with the OU outside of the UK, so they are used to dealing with it.
They charge more if you are outside the UK, but it's still not much in comparison to a degree from a "brick" university.
On my course we have online tutorials (in addition to face-to-face every couple of months...but there's no obligation to attend) and also telephone tutorials and people make good use of the forum. The online tutorials are conducted through "Elluminate" which allows participants to speak and the tutor to present slides. It's pretty good
Whilst I was in the UK I did a couple of other courses for personal interest (Islam in the West and Sustainable Scotland) and they were also both really interesting and well run.
Of course, it does really depend on what subject you're looking to study. If you have a look on the OU website there is a list of all subjects and you can even get a free "taster" of the courses through Open Learn
. The course description will tell you more about the assessment process. Some courses have traditional exams, but for others there is an end of course asessment which can be submitted online.
Good luck with your search