Yes, I fully agree with htg engineer. Once you have closed the valves, you will of course have to crack open the connections on the rad side of the valves in order to drain out the water in the rad before removing it. You will need to open the vent cock on the top of the rad to enable the water to drain out fully.
new olives will not be required - in fact you'd struggle to get the existing ones off the pipes anyway.
just one thing to note - if it's a towel rail that connects vertically to the pipes and there are no isolator valves fitted then you will need to at least partially drain the system. if a normal rad with side entry valves then no need to drain - just shut off the valves.
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