I e-mailed Richard Hall with that question, and this was his response:
There is basically a fixed stipend for us all, with an extra allowance to colleagues in London (because of the extra cost of living there) and small extra allowances for the Superintendents and District Chairs. But to all intents and purposes the stipend is flat across the connexion. The newly ordained are paid the same as those with 20 years experience, those who minister in small rural situations and those who lead ministry in large suburban churches. No 'career structure' at all.
I guess that there's no career ladder across the pond. It's an interesting idea, and would certainly discourage maneuvering with the Cabinet for high-paying churches or bishops punishing opponents by sending them to low-paying churches. That, and the system seems a whole lot more focused on doing the work of God. What do you think? Would the system work in America?