Do you have a citation for that? It seems pretty fundamental to the debate on this thread.
Looking at the Electricity Supply Regulations (section 49.4, parts (d) and (e)), the supplier has an obligation to allow the consumer access to their data:
(d) on request of the Customer at the relevant premises, it both establishes and thereafter maintains a connection through the HAN Interfaces between the Smart Metering System and each Relevant Consumer Device that is located within a part of the premises to which the HAN extends and is the subject of the request; and
(e) the connection established in accordance with paragraph (d) enables that Customer to access (at any time and, in the case of the Domestic Customer, free of charge) by means of each
Relevant Consumer Device, the Customer Information that:
(i) is capable of being stored in or held by the Smart Metering System (or any part of it); and
(ii) the Smart Metering System (or any part of it) is capable of sending to the Relevant Consumer
Device.
From that it appears that the supplier has to grant free of charge access to any data the meter can produce and the CAD can receive. If the CAD receives real-time data, the supplier has to make it available. It doesn’t mention anything about cloud services for this purpose and in-fact such a provision could discriminate against users who have no internet access (or have shared provision to which they are not allowed to connect new devices) so there has to be a non-cloud of providing access to your own data.