Martin Pentreath wrote:

to control the extractor fan in my bathroom. The idea is to put the
thermostat on the hot pipe going to the shower so that when the shower
is turned on it triggers the fan.

Why not use a humidistat, which would have the advantage of activating
the fan whatever the source of moisture - bath, shower or basin?

I'm planning to use 1.5mm twin and earth to make the connection
between the fan and the thermostat, which I think should be more than
adequate. But how should I connect the cable to those contacts on the
thermostat?

Those look like 0.25 in. blade terminals, so you need 0.25 in. insulated
crimp female receptacles, red or blue for 1.5mm^2. It's better to use
those on stranded flexible wire and connect to the twin & earth via a
suitable terminal block inside whatever housing you put the 'stat in.

--
Andy