Broken G2 missing theme: How do I change theme details if admin doesn't work?

I've broken my G2, an early beta, by trying to create my own theme without reading instructions. It seems that trying to upgrade to 2.0.2 whilst half way through making an attempt to skin it has messed things up. The upgrade gets to

step 4 and outputs an error:

"Configuration Error: Missing Theme

This album is configured to use the matrix theme, but it is either inactive or not installed. To fix this problem you can

install or activate this theme or select another default theme." it slao then does a huge Debug dump, which is too long to post here.

I've tried tinkering with my broken and evidently partially applied 'localTheme' via themes/locaTheme/theme.inc (a direct copy of the matrix one) but I've stopped as I don't want to make things worse.

It's worth noting that incentive to fix this rahter than toasting the install and starting again from scratch is about 3GB of photos already imported.

the FAQ says
"Theme upgrade - In beta-4 all layouts have been replaced with the new theme system. During the upgrade process the layout setting on all albums is cleared and the site-wide default theme is set to matrix. You'll have to reselect the default theme and any album specific settings to restore the layout configuration in place prior to this upgrade."

So, my immediate question is whereabouts in the data structure can I reset the setting that is obviously set to 'localTheme' rather than the desired matrix to one of the others, so I can at least get it working again?

Thanks in advance.

Installed themes:

Theme dir:
drwxr-xr-x 6 bealers bealers 4096 Jan 1 15:13 classic
drwxr-xr-x 6 bealers bealers 4096 Jan 1 15:13 hybrid
drwxr-xr-x 6 bealers bealers 4096 Aug 30 20:11 local
drwxr-xr-x 6 bealers bealers 4096 Dec 14 01:09 localTheme
drwxr-xr-x 6 bealers bealers 4096 Jan 1 15:13 matrix
drwxr-xr-x 6 bealers bealers 4096 Jan 1 15:13 siriux
drwxr-xr-x 6 bealers bealers 4096 Jan 1 15:13 slider
drwxr-xr-x 5 bealers bealers 4096 Jan 1 15:13 tile

Extended error from above:

Error (ERROR_BAD_PLUGIN) : Class localTheme does not exist

* in modules/core/classes/helpers/GalleryPluginHelper_simple.class at line 113 (gallerystatus::error)
* in modules/core/classes/GalleryCoreApi.class at line 187 (gallerypluginhelper_simple::loadplugin)
* in modules/core/AdminThemes.inc at line 320 (gallerycoreapi::loadplugin)
* in modules/core/SiteAdmin.inc at line 153 (adminthemesview::loadtemplate)
* in modules/core/classes/GalleryTheme.class at line 688 (siteadminview::loadtemplate)
* in modules/core/classes/GalleryView.class at line 285 (gallerytheme::loadtemplate)
* in main.php at line 287 (siteadminview::doloadtemplate)
* in main.php at line 87
* in main.php at line 80

System Information
Gallery version 2.0.2
PHP version 4.3.3 apache
Webserver Apache/1.3.26 (Unix) Debian GNU/Linux PHP/4.3.3
Database mysql 4.0.13-log
Toolkits
Operating system Linux toast 2.4.23-tft #1 SMP Thu Dec 4 11:57:36 GMT 2003 i686
Browser Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.1) Gecko/20060111 Firefox/1.5.0.1