I did two social science modules - Welfare, Crime and Society and Making Social Worlds. Making Social Worlds was my favourite OU course and also infinitely better than any of the modules I studied at a brick uni.
Welfare Crime and Society wasn't too hard but it was annoying, there was a 'key phrase' (entanglements) that popped up everywhere that drove me nuts.
I was already in a job when I started study so it hasn't had that much impact, but if you can, I would advise against doing an open degree, because I've found employers are curious about it in a bad way. I've had conversations like this in interviews:
"What did you study?"
"An Open Degree, so lots of things,"
"But what did you study?"
"Maths, social science, business..."
"So like A levels?"
Also, a lot is dependant on your tutor. Some are great, some not so. And take advantage of the forums, they will improve your grades as you get to iron out any kinks in your understanding with other students, especially useful in social science.