Dress it down then up then down then up

Heres the situation: I have two parties coming up (well there in november) and i need a dress. I'm only planning on buying one dress for both parties, because there are different sets of people at each party, so who's gonna know!

I want a dress that is kind of floaty, the second do has a meal involved and who wants to be restricted when you've got a buffet infront of you? I love the dresses Lily Allen wore in her video for 'The Fear' and the video for her and Prof. Green's song 'be good to me'. I think she and the dresses look gorgeous. I'm trying to find a dress under or up to the price of £20 ish, preferably under, ha.

Also, i'm liking this little one shoulder number below from Republic, and it's a lovelyyy colour, i love love love navy. I'm pale and navy doesnt scream that out to everybody, thats the reason i steer clear of yellow. Very draining ;)

£26.99 - Republic

I like this dress because it could be dressed up and down. The first party is a little bit more informal you see, so i want to be able to whack on a thin belt maybe? Swap my shoes. And in turn, be transformed from casually cool to 'something beginning with e' elengent.

ANY IDEAS?!

Love V xo