Unlikely to be possible. It might be a good idea to replace with a decent digital programmer switch. It shouldn't need any wiring changes.
If you already got thermostatic rad valves you might like to consider switching to a smart system, with electronic thermostatic radiator valves - say a Drayton Wiser system - that will let you control individual room temperatures. Payback time could be just 2-3 years.
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Drayton sm2 timeswitch?
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