I have been with them several months and will be switching ( peoples energy) (my E10 meter charged at E7 rates). They have been OK.
Note some small print from them that is of benefit.March 10th price rise.
“We do not charge exit fees at Economy Seven and you do not need to provide notice if you choose to leave because of this price increase. You are free to leave at any time but please be aware that a change of supply takes a minimum of 21 days. If you initiate your change of supply before 8th April 2019 and your start date with your new supplier is before 6th May 2019 then we will continue to bill you at your current tariff rate until you leave us.”