Although others in reviews report double billing issues when companies went bust maybe worth checking out. There will be prossible advanatages to havibg an intermediery to help with any issues, but could be draw backs. Make sure you use the exact forecast annual usage for you home, from last statement unless heating system / household change since. Don't use estimates else may not be best deal.
If you have time yourself to do price comaparisons that maybe better opion, but you will prob end up switching more often with SwtichD whihc can be better to get long term cheaper deal but may causes breakdown with customer support for long term issues, and possible confusion.