Thanks for your replies.
OK, first, to the respondent that doesn't know why I would want to do that? I am a home user, living in a safe environment (just my wife & I, few visitors...) & I've been used to being able to start my Linux boxes over the past 12-13 years in such a fashion. Admittedly in the early days I was using a GDM, but since I went to ArchLinux 10 years ago I have not used a GDM.
Yes, so xenodm, slim & the other GDM's are not the way that I want to do it. If using a GDM is the only way, then I'll continue to login & startx manually.
If there is a way via providing the appropriate code to ~/.profile (or anywhere else) then I'd really like to be pointed to a page where I can read how to do this (or of course to be given instructions here), as I'm sure that this must be possible?