I'm with Octopus and I agree they are generally very good.
The only negative from my perspective was their energy predictor which they were pushing last Autumn. It doesn’t take in individual circumstances and if I had followed their ‘recommendation’ to increase my DD to the levels they suggested then I would have overpaid by £100’s.
I would have eventually got the money back I don’t believe in lending energy companies large amounts of money at 0% interest!