I question I ask myself regularly! I did look into switching to Octopus, but at the time it was more expensive. I'm on Ecotricity's 24/7 100% renewable (ie they put an equivalent kWh of green energy into the grid as their customer consume, over a period of time) tariff, which is certainly not the cheapest available.
I can't switch to an Economy 7 tariff, because we don't have a smart meter. The company Ecotricity had installing them was absolute pants, they switched companies, and now they've got an enormous backlog of meters to switch out. Octopus wouldn't have us unless we had a smart meter already.
Luckily, the local shopping centre has a Tesla destination charger, and weirdly the ANPR system doesn't charge you at all if you park overnight...