Hi pranav I'm a current student and I am keeping an eye on this thread at the moment so this is the best place to post.
a) Keep it short and sweet. LBS folks know the value of brevity and hence provide tight word limits. If you did exceed, make sure its never more than 10%.
b) Visit
https://www.londonsa.org You will find not only the list of all the clubs, but also names and contacts of the organisers of the clubs. If you are not able to find anyone from a specific club send me a pm.
c) In a nutshell class of 400 is split into 5 streams of 80. You take all your first year classes with this group of 80 (same schedule / lecture halls). Within this group you are assigned to a study group of 6-7. You are effectively "married" to this study group. This group is socially engineered (i.e. it will be extremely diverse and you WILL have conflicts). Organisation within the group is up to the group members. Group assignments is collective responsibility.
d) R1 is definitely better for admission chances statistically.
e) As I mentioned earlier, stick to this thread.
Good luck.