Then the Hive / Hives are not controlling the heating, suggesting that one of them is not wired in correctly, or set up properly.
It's difficult because we don't know what you have done. If you can't resolve it, all I can suggest that you remove the Hives, put everything back as it originally was, and then when it is working properly, we can advise from the beginning on how to install the Hives.
Confirmed my suspicions. I've only wired the one in by the boiler. It's a danfoss ts715si, I've obviously mistakenly assumed it was a straight swap for the hive dual channel receiver. Do you have any ideas on how it should be wired in?