You seem to have one too many wires, the gravity fed system know as C Plan has altered over the years, first

then

and finally

the original there was no way to turn off domestic hot water, it was time only, then they added a thermostat on the DHW tank which allowed you to leave the heating on in the summer months to heat domestic hot water only, and finally a motorised valve was added to allow the DHW to be cooler than central heating water, but in all the versions just two wires to the programmer.
The Y Plan however does have an extra wire to programmer,

so the question has to be if using C Plan or Y Plan?
For the old C Plan the Hive works well basic the DHW contact works boiler and the CH contact works the pump, and once set to gravity the Hive auto turns on boiler when central heating is called for, however it does not work so well with the latter versions. Problem with Hive is with duel channel it is not volt free contacts, Nest Gen 3 does have volt free contracts but does not link to TRV heads, and it seems there is no one smart thermostat that will do all, so you have to select the smart thermostat depending on your system.