Octopus Energy are accepting new customers again and they still have their offer for a £50 credit off your first bill from a referral (referrer and new customer split £100).
My link is
share.octopus.energy/ashen-jade-551
or you can quote "Ashen-Jade-551" on the phone/chat/social to switch
With the cap the same for everyone (not on a fix) this is literally free money for switching.
Or if you have an electric car, they have some great rates for overnight charging so money to be saved there too.
Disclaimer: I get a £50 credit on my account too, but once you're a customer, you can then share your code for others to use and get even more off your bills.
And I have to say I really rate Octopus's service, interface and billing. Enter your readings in the app and an accurate bill is generated within minutes so you can really stay on top of usage even without a smart meter and you can set your DD amount yourself.