I tried this about 2 hours ago now. Your suggestion seemed to sort the light problem at least initially. However, while the freezer reading on the fridge door soon moved from -18C to the default -20C; the fridge reading has remained at the 9C mark, the intermittent pinging remains, and when I tried a few moments ago the internal light in the fridge no longer works.
Any other suggestions?
We phoned the Samsung agents who live at some distance from us. They indicated that the problem probably lies with the 'Read switch'. It was my wife who made the call so I'm not sure if that should be 'read switch' or 'reed switch'. It looks as if the 'read switch' may be thinking that the door is not closed which is why the bleeping sound continues and why the light goes out after a certain time. Do you know where this read switch - or equivalent - is to be found on the Samsung RL58? Could it be in the electrical bits that I had to disengage and then re-engage at the time of the door switch - electrical cables had to be switched from one side to the other of the top of the fridge?
After speaking to the person at the Samsung agency, I had another go at tampering with things tonight and have managed to sort it without requiring a visit from their service engineer, so I'm happy with that. Many thanks for your help.