Hive wiring doing it myself?

Hanzkbar

Recently acquired 2x Hive mini for Combi boilers for two regions. What i have in the property is BoilerMate OV A Class thermal store & Viessmann Boiler & 2x Drayton Digistat +3 thermostats (one for upstairs and one for downstairs). 

Attached images show wiring on thermostat and the connection box next to Boilermate thermal store. 

Guessing in this scenario; the wiring in connection box dont matter? As i am replacing thermostats for heating only. Intention is that the hot water carrys on as it is via Thermal store & hive thermostat is for Heating only. 

The current wiring in Digistat is as shown in picture. I found someone else online trying to do the same thing as me with wiring as shown (third photo - hive wiring). Its a different brand but guessing the wiring is same in Digistat thermostat. 

Plan of action is to do the same; 

N from thermostat to N in hive
L from thermostat to L on hive 
and run a loop between L and 1 of brown wire.

i dont have earth in mine. Dont think it matters. 

Any help will be great. Hive is charging £120 per thermostat which i think is crazy amount considering if i am right its just a direct swap of thermostats and ensuring cables are connected correctly in thermostat.