So then I thought, let's be brave (for me), before upgrading to Jesse I'd try upgrading my poor broken Wheezy desktop. So I sort of followed the advice on LinuxG, but instead of sudoing all the time I opened a root shell and did:
$ add-apt-repository 'deb http://repo.mate-desktop.org/debian wheezy main'
$ apt-get update
$ apt-get --yes --quiet --allow-unauthenticated install mate-archive-keyring
$ apt-get update
$ apt-get install mate-desktop-environment-extra
Very nice, just a couple of issues:
First, the MATE desktop help is broken, I am getting "package not installed" type messages. Any ideas on how to fix that? Specifically, I want to move the bottom panel to the top of the screen.
Secondly, in the synaptic Software Sources dialog (Settings > Repositories) the tabs and most of the tabsheet contents are white text on a pale grey background, quite unreadable. A few tabsheets have patches of black text. Any ideas on what options to change to get black text throughout, and where/how to access those option settings?
Plan B is to try installing the more recent Jessie instead but if it suffers the same issues I'll still need answers.