Good to hear that London is OK for busking. I find that much of not geting hassled has to do with knowing where to busk, and I never got to know London well.
As to licences, I have, as a matter of morals, never purchaced a licence to practice that trade that has belonged to us for thousands of years. We have always had a first get there - get the corner rule in Busking. One day, a few months ago on the Subway, and older gent gets off the train and comes over to me, and says, We have this spot in ten minutes. I look at him, as though he is daft, and say, Well, ... I dont think you do!? He pulls out a licence from our esteemed murderer, I mean Mayor, and says it is a BUSKING LICENCE! Well, I pack up and tell him that I never thought I would see the day when one busker moves another with a piece of papaer. As I told him and his mates, it is nothing but scabbing, and turning over the freedom of our trade to a government who has never had a part of it.
Larry