I don't see how an OU course is any different from a regular uni course, in both you need to keep up with the reading, manage your own time and motivate yourself to do the work. If you don't you'll fail. I could definitely do that no problem.

Tour guide was probably not mentioned as many countries have very stringent rules and regulations around guiding - ie they prefer to keep that type of job for their own nationals. Again - work permits are often required - even for tour leaders who are really only company reps. The rules are complex in many countries and often it is not possible.
If you do an OU course just make sure there is a realistic chance of finding employment at the end of it and try to find stories from people in that career first. I say that as you may end up completing your course and finding it very hard to actually get into any job and back to square one.
I know several people that completed their Master degree at the same time or before me and they haven't been able to find anything to go into. Higher education is worth it in the long run, but for the next few years it's going to be tough without previous experience in that field, especially if it's something you've not worked at before.
I'm not saying don't do it, just make sure that you think of life after and if it will make you happy and be able to give you the change you need.
