To be honest, at the end of the day which college you end up in doesnt matter a huge amount after freshers week! Go for the type of accommodation you want, so if you want standard, then Bowland, County, Furness or Pendle, ensuite, any college. If you want to be in the centre of campus, then Bowland or County.
I know county main was refurbished last year, and County South is being done this year, but I am not entirely sure wether they are still standard. I'm pretty sure they are. Standard rooms tend to be a little bigger than ensuite, and are obviously cheaper, by about £20 a week.
Oversubscribed colleges.... umm, differs a little each year, I think.... Furness is usually pretty popular, almost everyone I know put Furness down in their choices, very few got it. I know two years ago Bowland was pretty undersubscribed, don't know about now.
As to the maths and politics, I'm pretty sure you can unless there are timetable clashes. You can take, to the best of my knowledge, any course with the right number of credits, so long as it doesn't clash with your major, no matter the faculty.