I think that is a volt free stat which means it just switches whichever voltage is supplied to it by a boiler or programmer but it might have a mains voltage supplied to it to make it operate. Carefully take it off the wall and see if it has 4 wires going into the back of it.
You can test it with a multi meter by checking that you have continuity across the contact terminals which make and break as you turn the knob.
Drayton, make a range of thermostats. Unfortunately for you they all look very similar from the front.
From the diagram below; If it's a RTS1,2 or 3 it will be 230V only. The RTS4, 6, 9 or 10 needs a 230V supply but the control side can be 230V or volt free.
With models RTS1, 2 or 3 - linking terminals L and 3 together would by-pass the thermostat and put the heating on.
With models RTS4, 6, 9 or 10 - linking terminals 1 and 3 would by-pass the thermostat and put the heating on.
These thermostats are generally very reliable though and there are many other components of a heating system that are less so.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local