OK, have got it sorted. When books are converted I can't seem to change the file name format that they are converted to, but when I then save the book to disk I can edit the file name format. Seems a strange two-step process; first convert book which is saved to disk in calibre's own name format then save the book to disk again but with my file name format. Can't understand why the two steps could not be combined and have the convert save format modifiable by the user, but since I'm a 100 miles ahead of where I was I will take this as a win since I can now continue using calibre and save myself considerable time and effort.
Thanks again to those who helped.