As said some of the downloads are not gpx files, but some are. mm won't open them but easygps does. Then save as gpx file and mm will then open it. Don't know why mm doesn't open in the first place but there we are.
Thanks Jester but I have followed your suggestion with no avail.
Now on this site, pick a route and left click the gpx link and the 404 error message comes up. So right click and save link on the desktop as gpx file. But memory map doesn't want to know it even when open!
If other members of this site can open these files then must be my mm version or settings?