Any husband is always wrong.
There are a few possible explanations.
If the radiaotr gets hot at the bottom, there may be air in it. Have you tried bleeding it?
The thermostatic valve may be stuck. You can unscrew and remove the thermostat part and you will see a metal needle protruding. Try moving it in and out - but be careful not to pull it out completely.
Your heating system may not be balanced, so all the hot water is going to the other radiators in preference to the bathroom one. Did it work better before fitting the thermostatic valve?
Does your bathroom radiator come on even when the rest of the central heating is off? Does it get hot whenever the boiler is heating your hot water? If so, it may be a bad idea to fit a thermostatic valve because the rasdiator provides a path for the hot water when the hot water valve closes. Not all systems work this way, but some do.