I’m not one to give up so easily, so just want to clarify you mention I need to find the hw on and off wires in the cupboard, can you please just confirm my understanding below.
If I locate in the cupboard the two wires that connect to the hw on and ch on (these are the two wires in 3 and 4 on the Honeywell), then find in the cupboard the two existing stat wires and basically connect these up so I have two wires running from the stat which will be the ch on and hw wires in the Honeywell clock and these then go in the T1 and T2 of the nest making the 12v connections.
I then put all the clock L and N into the 2 choc blocks and have a single wire from the N block to the N on the nest and same with live but then have a second live to number 2 on the nest (manual mode I assume this allows you to turn the heating on pressing the heat link button on WiFi outages)
Is this all correct?
If so I assume I can use a length of cable and multimeter to do a continuity test on each of the wires to locate them.