So I’ve just had a reply from the makers of glow which suggests the supplier (Bristol Energy) need to put a request in with the meter manufacturer (Secure) who implement the change. Not sure if the change mentioned is specific to the glow CAD but hopefully will make things easier from July.
"… To give you an idea of the lay of the land here, we’ve found utilities have been very resistant to opening up the HAN, for a couple of reasons.
Firstly, they have tried to claim it is a security risk, or that it is not company policy to allow a third party device to connect to their meters. This is a) not true, our device is certified and poses no security risk, and b) Smart Meter licensing obligations require them to allow the connection of third party CADs. Like I say, we have had resistance, however we’ve had a little more success with smaller utilities, which will hopefully be a positive in your case.
The second reason they have given as refusal is that currently, Secure charge a £500 fee for whitelisting runs (whether it is 1 CAD or 1000). Although this is a small amount for a massive utility, the Ombudsman recently sided with the utility when one of our customers went to them to try and help get the CAD joined. However, we have been working with Secure on this point and they have developed some functionality for us which will dramatically reduce the cost of whitelisting runs. This is in user testing and should be fully available on the 16th of July if all goes well. This may not mean utilities immediately agree to open the HAN, but it removes one of their significant arguments against doing it."