Galactic Civilizations II: Endless Universe is available from play.com for £4.99 (75% off the retail price).
Not to be confused with Galactic Civilizations II: Ultimate Edition:http://www.play.com/Games/PC/4-/6134919/-/Product.html?searchstring=Galactic+Civilizations+II%3a+Ultimate+Edition+&searchsource=0
Galactic Civilizations II: Endless Universe =
Galactic Civilizations II: Dark Avatar + Galactic Civilizations II: Twilight of Arnor
Galactic Civilizations II: Ultimate Edition =
Galactic Civilizations II: Dreadlords (main game) + Galactic Civilizations II: Dark Avatar + Galactic Civilizations II: Twilight of Arnor
Endless Universe is really just the two expansion packs although the original Dreadlords missions are supposedly accessible from what it says on the Wiki:http://en.wikipedia.org/wiki/Galactic_Civilizations_II:_Endless_Universe
However, from a review on Amazon someone says:
Be warned, this is a specific compilation of Dark Avatar and Twilight of Arnor and doesn't include the original campaign from the first release of GalCiv 2., however that's no real loss as the original game was fundamentally changed with patches to make it better but the campaign got a little borked in the process. What's offered by way of the two expansions is all you really need.
Galactic Civilizations 2: Endless Universe is a comprehensive, standalone expansion pack (no full version required to play) for the best-selling and award-winning space strategy game. Endless Universe builds on the epic story, following on from Dark Avatar and Twilight of Arnor - two expansion packs which have never before been released in Europe. New challenging and comprehensive campigns and units, as well as an improved visual appearance will give you the ultimate experience of conquering the Universe!