How do I work my heating?

I have a Randall 102E monitor in my kitchen and a thermostat thing in my lounge. I have a gas heater (which makes a lot of noise) and my water works from a boiler tank in the bathroom.
I am South African and all this stuff is new to me and I have a horrendous heating bill as i dont have a clue how to work all this stuff.
If i google the Randall 102E monitor I cannot find the model i have and i do not have a clue how to work it. I thought I had it bagged to just keep the water warm and not have the heating on but it doesnt work.

Please help