[daveeb]

I changed from Eon to Octopus a couple of years ago, so can't comment specifically on Bulb, who were actually my other choice. Can't remember why I went with Octopus, but they have similarly good reputations.
I didn't have to contact Eon, I did have to provide octopus with a final reading. Eon will send you a final bill or reimburse depending on your balance. Can't remember the time scale exactly, don't think it took more than a few weeks.
Smart meter should be optional, it is with Octopus currently. Don't think I'd sign up with someone who enforced one.