re: Beagle 2
Probably smarter to instead focus on the Moon- let the pros at JPL handle Mars. Not that landing a vehicle of some sort at the Poles would a walk in the park- esp if they want to do something ambious like drop one in a dark crater. [Btw, Spacedev is looking at idea of a lunar lander:
http://www.space-frontier.org/cgi-bin/BBS/MoonBase/read/1006 ]
This isn't going into a dark crater, but if you wanted to do something that did and are looking at something around Beagle's price tag (even cheaper) and your interest was mostly finding life beyond Earth, you could take a stab at the dark- why not go where no one has gone before:)