Of course sign up figures don't necessarily translate into votes. I suspect a lot of people have signed up to try and put the wind up labour.

Personally I don't particularly trust Corbyn as leader. He likes to think of himself as uncompromising but really he's just awkward, hard to work with, and let's perfect be the enemy of good far too often. But his party is useful in trying to show labour how unhappy we are with them.