I find Octopus pretty good. We were with the Co-op before them - and so we've had a smart meter for something like 5-6 years now. And that means (generally) no estimates - so their predictions have been based on 5 years' past usage, which has been pretty even and regular. I'm prepared to...
Nothing but praise for Octopus and their levels of service:
Easy-to-use website
Helpful staff who always respond - often with more than I asked for
Smart Meter has never been a problem
Can change my payments whenever I want. I'm 'in control' in their language
Quite fun for a large...