I am going to install a thermostat for frost protection of my CH system
mainly because the boiler has now been sited in the garage.

I think putting it in the garage will not do as in the winter the
temperature of the garage will not rise significantly and the result will be
it will over-ride the room stat settings causing the boiler to short-cycle.

I thought of the hallway particularly on an outside wall so it should detect
the as near as damn it the same temp that the garage should experience yet
it should switch off once the temp in the hall has risen. My main concern is
that the temp inside will drop off much slower when the heating is off
compared to the garage and the stat will not not fire up the system quick
enough.

Richard