Hello
Well, when I did it it was just a 30 point course and there was no summer school. Think that was on the next course. So, can't comment on that bit. I had done (and failed!) A-level French about 20 years earlier. However, at the time I did L120 (and the reason I did do it, tbh) was that I was having private French tuition - only 1 hour per week. I'd been seeing my tutor for about a year but felt I needed a course to give me some structure/reason to continue. I did also go to as many of teh 3 hour monthly tutorials as possible but less towards the end of teh course (when I felt some people had advanced more quickly than me...) Anyway, the TMAs were a mixture of listening to a recording and then having to write a piece covering some of teh aspects that you'd heard. Plus, there was a piece to read from which you then had to record yourself speaking about. (only for 2/5? (can't remember exactly) minutes)
The exam consisted of submitting a piece of writing (you had plenty of time to do it) and an oral exam. For this you were given notice of teh subjects to talk about and you had to speak in your group for 2 minutes (longer than it sounds). The other group members did likewise and then you had to have a "debate" for a further 8/10 minutes. Unless you were totally mute in this bit, you'd be unlikely to fail.
Fortunately, because I had a French tutor, I was able to go through my TMAs with her - she helped with the listening bit (my weak point) and she reviewed my final written exam bit for obvious errors (agreements, etc) but I didn't use her for style or content - just to explain more clearly the areas I was weak on. Presumably the OU tutor would also have done this but easier for me to use my personal tutor.
I really enjoyed it; it was my indulgence for no end purpose. I just like French and wanted to improve it. Have to say, 8 years later I feel as though I'm back to where I was pre-course but by the end of the course (and certainly after the Sat tutorials) I did feel so much more confident and able.
Hours per week depended on when teh TMA was due. I could spend a long time on the written bit - a couple of hours each night in the week it was due. Other than that, probably just my weekly lesson?
Hope that helps and ask if you need any more info.