Jana over at her blog http://hijabstyle.blogspot.com/2008/08/party-abaya.html put together this look a long time ago. All I've changed from her set is the shoes and I've added a niqab. Meerah, if I find a plainer abaya of a similiar shade I'll edit this post and add it here so keep checking this post.
Sommia abaya £44.95, Alkaram Direct; silk pashmina £14.99, Scarf World; gem clutch bag £12, Debenhams; carved flower ring £7, Dorothy Perkins; flats, Lanvin; Niqab http://www.zainabsboutique.com/brown-3-layer-niqa3.html for $15.99 USD.
Meerah's Inspiration: a munaqaba from Bosnia, pictured below