Ofgem has lots of help and advice for households, including how to make a complaint about your energy supplier, and what to do if you can’t afford your energy bills.
Age UK has a good explanation of what happens when your energy supplier goes bust, and sources of support for paying energy bills.
Simple Energy Advice has lots of links and tips.
The Energy Saving Trust have lots of tips on how to reduce your energy usage.
The Money Saving Expert website also has lots of useful advice.