In reply to Sharp:
I've had isues with Bulb. I used the comparison sites armed with the summary of usage from my existing supplier. Bulb came up £200/yr cheaper. (gas and electricity) so I changed supplier. Within 2 weeks they had a price rise. As all of the other suppliers were going through that phase and that it was still £100/yr cheaper I sucked it up. Then two weeks later they claimed that they had been provided with third party information that required them to increase my monthly payment. Based on the fact that I'd provided actual third party info at the time of my search I questioned this. Their main reason was to ensure that I built up enough credit (roughly 2 months) to cover fluctuations in the tariffs and temperatures. Their new monthly rate was £1/month more than my previous supplier.
After protracted discussions they have gone back to honouring the original monthly fee with the rider that I need to be aware that I could be under paying and will be required to make up any shortfall.
With the predicted £200 savings I bought an energy meter for £35. I've used this to weed out all of the little things that are on all of the time for no value that were burning electricity, only pennies, but over a year it'll make a difference.
Bulb have recently reviewed and modified their charges. They have juggled with the standing charges and the energy unit costs. I'm still with them to see what happens.
Good Luck