You mean like the one in their FAQ.
FAQs about Octopus Go, the tariff just for EV drivers
In exactly the same way that a 10pm TV programme will always be at 10pm etc etc...
This is how Octopus has worked for the last 4+ or so years that I have been an Octopus customer. Its simple. 00:30 is always 30 minutes past midnight, irrespective of whether it is GMT or BST and 04:30 will always be 4h30m past midnight except twice a year when clocks change, when it will be an hour later, or an hour sooner, and yes, you get an hours more charge in October and an hour less this Sunday. Anyone on Octopus Go (00:30-04:30) can confirm this by checking their itemised bills - they will have 5 hours cheap rate last October and 3 hours cheap rate last March.