How to wire a room thermostat?

Hi, i have a Ravenheat csi 120 (t) low nox combi boiler but there is no room thermostat so i have bought a Salus wirless digital thermostat with RF (RT 300rf).

My problem is the instrucions for wiring are simple enough but i am unsure of which wires in the boiler to use.

On the main board there is a room thermostat block with 2 points which have a 1 wire loop.

on the thermostat there are 5 points SL(off), live in SL (on) Neutral and live, both lives are linked.

Please could someone help, i have had my cousin (an electrician) around but he has not done one, but did explain how i should do it...but i am still confused....he did check with a meter on the points in the boiler and said it could be volt free.

Please help me....i am usually ok with things like this but this has me stumped. :(