Planning permission would be needed .gas and electrics could be a problem, separating existing supplies like wiring and water / heating. building regs to comply.
Don't underestimate the cost of all of this
Simplest solution would be to have dual towel rail that is heated by electric as well as central heating.
The other solution would involve altering pipework and installing zone valves which would no doubt be much more expensive
Or just turn off all the other radiators