used a derby for first time this week when rendering internally. It was ok, just different. As for the radiator you have choices. One of which wouldnt be leaving it on (not if you want it to look good anyway).
If the pipes are coming out of the loor and are poly (plastic) then just lift the rad off its bracket and lie it down flat on its front. Taking care not to damege the rad or the pipes. If the pipes are copper then turn off your rad at the valves at both ends then undo the nut on either end too. have a water catcher ready as there will be no water coming out of the pipes but your radiator will be full and will empty. Top tip if your doing this on your own, once valves are undone put your finger over just one of the valves and the water wont run out.
All this can be difficult on your own and is a lot easier with two people