[K12OSN] howto restore desktop settings

[Gavin Chester]

<sheepish> I have lost all my desktop tweaks for both KDE and Xfce by
accidentally choosing 'reset desktop' at the session login screen
(GDM?).  Groan.  How do I restore my customised settings?

I know they are all there, but they appear gone when logging in.  For
example, evolution treats me like a new user, whereas I can see in
my /home that the two accounts I had setup and received mail on are
still there. 

I know it's one of those fundamental things one should know, but I've
never been in this spot before, so .... Help!!

Gavin.