Thank you Russel for your sage advice. To answer your questions, my camera is five years old, has not been subject to shock, has been operated under normal UK temperatures and humidity conditions. It has never got wet and has never been used in hostile environments.
So I am now going to carefully follow your suggestions and will report back on results in due course. Thank you again and please accept my apologies for this tardy reply occasioned by an unwelcome flu-like lurgy which has now thankfully abated.
I've followed you advice to the letter Russell. So far no joy. However, there's still one of your tips I still have to explore. I have yet to try a new battery which I will order shortly and I'll be in touch later to inform you of results.