I'm with Octopus having been moved there from Avro last November. I'm still on their 'ex-Avro customer' variable tariff, which nevertheless looks better than anything else they are offering. I looked at Octopus Go a while ago and it was 5p/unit for just 4 hours in 24, so you'll get a tad under 30kWh for £1.50, but the rate for the remaining 20 hours was quite a bit higher than the standard tariffs, so a net loss.