I'm using Octopus, who are the only supplier to have successfully extracted data from our smart meters (first installed by nPower, then replaced by Robin Hood because incompatibility, who never got any data from them and misleadingly used estimated readings for years).
Green energy, reasonable prices, and an API that lets you access the smart meter data via the internet. If you can make reasonable use of it (we can't), they do a tariff that reflects the wholesale price of electricity at 30 minute intervals (it occasionally goes negative on windy nights). Their website is suspiciously good for accessibility, too.
PM if you (or anyone else) wants a referral code.
I also hear good things about Bulb.