Phew! After reading the site that Phil suggested I re-read all of Dr Whatsit's warnings and the deep care that should take place when cleaning, including the painstaking procedure. I was really worried that I would ruin the coating.
Then I went to Arthur's site and it recommended Windex, with the statement that all the coatings are able to withstand stuff that is not corrosive! Chee!!

Confused? A bit but its what I wanted to hear (read.)
So then Rod pipes up and tells me what Don Whitman said and I began to relax a bit more. Next comes Roger whom I know quite well and I finally thought, "Ah! To heck with it!' Pulled the OTA into my study with the Bintel 'snake oil??' and cleaned it gently with some very soft material that I got with a pair of sunglasses once. Dried off with Kleenex man-sized tissues (very butch I am!) used the brush on the end of one of those puffy 'thingys' to get rid of the left-over dust from the Kleenex and voila! It looks like a bought one! No scratches on the surface but there are one two pin prick size 'gaps' that I won't worry about. And I won't ever worry about it again.
Thanks fellas,
Bert
PS. If I was still in WA I would let you use some of my 'snake oil' Roger!