I heard there are two expansion packs for GCII I have a physical copy of the 'dread lords' but learnt of 'The dark avatar' and twilight arnor' Is there anywhere where I can download these two expansions (as I already have dread lords installed via CD)
No, the expansions are no longer available separately. If you want them (which I can only advise, as they add quite a lot to the game), you have to buy the Ultimate Edition.
Finally (might as well ask this) a lot of the layout of the menu for the game and the 4x gameplay is bit like 'space empires' was space empires or GCII a copy of the other?
No, they're not. Well, at least as far as I know. Of the Space Empires-series, I've only played SE IV, and I can't see any similarities between its menu layout and GalCiv 2's. No idea, if that changed in SE V, but that game came out after GalCiv 2, as far as I remember.
As for having similar gameplay, that's what I would expect. They are in the same genre after all. Still, I'd say GalCiv plays more like a combination between MoO 2, Ascendancy, and Civ.