Single channel hive for Grant Oil Boiler

[Nihad]

You have already noted cable you have circled blue is to thermostat just don't couple it up . I would replace that cable with a 3 core into fused connection and then to hive .
I take it the 5 core circled red goes to boiler?
I'f so connect as above with a single channel hive you will have one core too many just make spare electricity safe.
You don't need anything to ,20 that's a permanent live feed through board.
Room stat connection needs to be linked.

Thank you so much this worked, l had to link 25 to 26. Also switched CH button on the boiler to Timed.

Also managed to disconnect the switch old thermostat now l do have 2 extra cable core. I will replace it with 3 core cable.

Thanks everyone.