Same as for non-thermostat radiators, with one extra.
You need a 'service cap' which replaces the body of the thermostat and
converts it into a normal valve, so it can be turned off completely.
Sod's Law states that you will not have one, I think a previous thread
mentioned where to get one, if not try your local plumbers merchant.
Packing out the space between the head and the valve with small coins to
force the valve shut has also been mentioned.
'Frost Protection' setting (normally '*') is probably all right in the
summer, but refer to your copy of Sod's Law.
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