No.
It will be connected to your boiler which heats up both your central heating (radiators) and your hot water but they are on different systems.
So your radiators may not work but your shower would still work, unless the ignition isn't working then neither would heat up (assuming you have a combi boiler, an immersion system, I think, would still work as the rads and hot water are heated by different sources).
The water in your radiators will probably have chemicals in to stop it getting all gunked up and definitely wouldn't get you clean!
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