they each have their advantages - on the course at csm i hear you do a lot more work so it's quite intensive, but i'm not sure how good the tutor/student ratio is (as the college isn't renowned for this). you can specialise right from the start, or if not i hear the diagnostic stage is very brief. other than this i don't know much about it!
ccw/camberwell (i recently finished my foundation here) is probably the more traditional approach to the course in the sense that you explore all the different pathways before specialising. i think that students get the most space on this course as foundation students have their own building with a traditional print room, 3D workshop, and IT facilities. you also have the unique option to specialise theatre/screen/set/costume design at wimbledon. i personally loved the course here, best year of my life!
lcc have the smallest course so i'm guessing the tutor/student ratio is the best here. you have to specialise in an area (film, graphic design, photography etc) when you come onto the course but this doesn't limit you - you can do anything you want! a friend of mine just finished the course there and specialised in textiles, she really enjoyed it too.
you can apply to halls (i did, in fact almost everyone in my flat was on the course), but you won't get student loan as it's not a degree. if your household income is low it's possible to get a bursary - my flatmate did this and got 2 payments of £2,000. if you're under 19 you don't pay tuition fees but if you're 19 or over it costs £3,500 which you have to pay yourself. open day dates will be on the website, i recommend going to all three to make an informed decision. good luck!