EDF is a very large French company, so I'm surprised you haven't heard of them. Check your usage at gocompare, or similar, and see if it's worth changing, bearing in mind that you might have an exit fee.
EDF is one of the 'Big Five' energy suppliers (alongside British Gas, Scottish Power, SSE and nPower/E.ON). Their prices are likely to be largely in line with their major competitors.
If you're looking for a supplier with solid 'green' credentials (and good reviews too), check out Octopus:
https://octopus.energy/