This looks like you have single channel receiver wiring for heating only
So from left to to right you would map this to the Nest Heatlink:
0 (blue) -> N (neutral)
1 (brown -> L (live) and also bridge to Nest terminal 2 common
2 (grey) -> make safe with some heat shrink or electrical tape
4...
This was the location of the original Hive receiver - I just pit the Heatlink in exactly the same place and put the Thermostat below so if could power it off the Heatlink. It's reasonably centrally located in the house so seem so ok to me.
I've just moved house and there was a Hive 1 installed. I could not for the life of me get the thing to register so I could control it online and I've previously used the Nest system. The price difference between upgrading to Hive 2 or Nest was similar so I chose Nest without install because it...
I currently have a Hive Active Heating 1 system installed that I would like to replace with a Nest Thermostat v3. I think I understand the wiring but I'd like confirmation.
The Worcester Greenstar 24Ri boiler and hot water tank are wired into the Hive receiver as per the following diagram...