Many thanks to everyone who has responded from around the globe setting me straight on log tans on a pocket calculator. Like most things it's easy when you know how - and now I do - several times over :-)
I'm leaving things for a day or so in case there are other replies and will be in touch individually very soon. My special thanks to those who run this wonderful service. I couldn't get the help I needed in my vicinity but within a few hours it flooded in from around the world! Thanks again to you all. Tony
