Hmmm, rules wise, you might be able to run with . A whiles back Games Workshop decided to put the rules up on the web as free downloads.

The fluff is wrong, but the rules are very much PA. Mutants, gangs, religious loons, and natives. Changing the fluff should be pretty easy.

The Auld Grump
*EDIT* Fix da linkie...

It's not "nuclear apocalypse," but Dark Age might work if you're looking for a post apocalyptic game and not necessarily just something to use on Urban Mayhem stuff, as it's set on another planet in the future. It's a great rules system and the majority of the minis are awesome. Only problem they seem to have gone into hiding for the time being. I haven't heard much about any new developments in Dark Age for a long time.

Dark Age is still going, though a bit slowly. Air Caste and Outcast factions are coming up...... not really the game to suit WWG Mayhem scenery though (Mars Station, Caveworks, Hinterlands, Hellworks etc would work better)...... you can do a great 'Ghosts of Mars' game with WWG Mars Station and plenty of Dark Age Buzzblade figures though

I would look at 'Savage Worlds', they have a number of 'post-apoc' settings available including the 'Necropolis' setting from Triple Ace Games, 'The Day after Ragnarok' by Atomic Overmind Press, and the memorable 'Low Life' by Andy Hopp. You also have 'Evernight' which is a post-apoc fantasy setting.

Takes very little work to make them skirmish games especially with the Savage Showdown miniature rules.

Another option, from Precis Intermedia, is 'Earth AD' which can be modified fairly easily into a skirmish game.

Mutants and Death Ray Guns from Ganesha Games might suit you. It is a quick and simple to play system with a campaign element to it. It also uses any figures you might already have and can be played with very few figures, so you can get started quickly.

As far as miniaks go... Lots to be had on the interwebs.

What exactly are you looking for?

Nuclear Renaissance? use the minis you want and not the gargants in the "official" range.
No Future.
Skankgame (aka Warlords of the Wasteland 2085.)

Wastelands?
Perhaps poke around here for a bit: http://s1.zetaboards.com/Post_Apoc_Wargames/index/
and read a few batreps and reviews.

Day After Ragnarock is more of a setting than a system, I believe. (At least, it's available for multiple settings.) That said, it's AWESOME. At some point (soon!) I'm going to run it with Barbarians of the Aftermath.

Have to agree with you about Savage Worlds - more time spent on the story and play, less on the stats.
As for skirmishing, the official Savage Worlds skirmish rules ( - immediately after the core rules) are good and free!

I have been following a Savage Worlds Campaign based in the world of Fallout - the site is:

He used to post every week, but something has slowed him down recently. He also uses lots of WWG terrain - I see the original Streets of Mayhem, armory, and other sets.