don't do bands, i just set a day rate for each task involved. if i'm giving a client a discount then i tell them, and its usually b'cos they're good people or its interesting work. then they can't be surprised when you raise it.
if its a job that i know is going to be a pain in the arse then i try and price it out, that way at lease if you win it you know you're being paid well for it.