Unfortunately it's difficult to see enough detail from the photos to be 100% certain, so you should check carefully that my assumptions are correct and that the cables actually go where I think they do. If in any doubt don't proceed and post back.
1) The 230V mains supply cable should be fairly straightforward to locate. It should come from a 3A fused spur and connect to the Danfoss 103 terminals 5(N) & 6(L). It will probably be the cable with the red and black wires in terminals 5 & 6, but please check to be sure. This 230V supply will go to the Hive N & L. So, no surprises there.
2) Identify the three core cable that currently goes to the existing Honeywell room thermostat. That will need to be removed completely as it will no longer be used. It should presently be connected to the Danfoss terminals 1 (red), 2 (yellow), and 5 (Blue). If you have anything different, post back.
3) Then there should be two cables left. One cable will go to the pump, (connected to Danfoss terminals 2 and 5) and the other cable to the boiler (connected to Danfoss terminals 1 and 5) These cables would be removed and reconnected to the Hive as per my diagram. The wires presently in terminal 5 are the neutrals. [Some, but not all boilers also require a permanent live, but I don't see this in any of your photos]
4) Don't forget to reconnect all of the earth wires. Whilst the Hive itself doesn't need an earth connection the pump and boiler do. So use the Hive 'earth tether' to connect them to the supply earth.
I mentioned the limitations of your system because some think that by fitting a Hive / Nest etc., to their old system that it will provide the full functionality and are disappointed to find that the limitations they had before are still there.