Well, I finally did it, got Network Manager working on Mint 12 just in time for Mint 13. Oh joy!
Had to change the wireless card and use a hacked bios as Thinkpad bios has a whitelist for "approved" cards. I went from an Intel 5300 to an Intel 4965 to an Atheros AR5008X before finally getting something that worked perfectly in Mint 11 to do what it is supposed to do in 12. I even have "N" speeds bearing in mind your version of "N" may be different than mine!-
Apart from the bios I also had to perform a little surgery on the laptop base. As the X200 can also take a mini pci card there are two extra standoffs for screws which foul the underside of the Atheros card when it is installed. These can be easily removed using a gentle but firm sawing action with a pair of small snips. Wear safety glasses while doing this as the standoffs come off at some speed!
X200 bios download- http://forums.mydigitallife.info/thread ... ad/page392
Atheros wireless card fix- http://www.unixmen.com/resolve-slow-con ... y-narwhal/ (You just know it won't work "out of the box")
Hopefully and despite my obvious sarcasm this will help somebody else in the same situation.
On the off chance a Network Manager dev might read this....any chance of a fix for Intel cards please!