Okay this is the ball game. First of all yes, it is possible to get a pupillage with a 2.1. Off hand I don't know about a 2.2 but it's fair to say the chances drop sharply.
Getting a pupillage involves two challenges. The first is getting through the door to an interview. This is the hardest because it is capricious. No one can really know how a Chambers knock 200 or so applications down to 10, or however many they have shortlisted for interview. So it's fair to say a 2.1 is a great start, as is a VC from the BVC, as is mooting experience and mini-pupillages.
After that, if you get an interview you have a chance to shine, and that's when it becomes a little easier. The interview may be hell but at leats there is a feeling that it is in your own hands.
Couple of extra points having read the posts- glad to see so many people talking about Norwich Law School- a temple of law!
Also to the chap who seems obsessed with talking about him/her self in the third person, it's 'Chambers' and not 'firms'.