craftgrrl | Halloween Question!

Hello craft girls and guys! First post here, but I'm afraid it's a question. I looked through the memories first and couldn't find anything, but please do tell me if I've missed something!

I just decided to go to a Halloween party tomorrow, and the theme is Rocky Horror. After a bit of Google-fu, I've settled on trying to dress up as Columbia. I've never made/bought a costume before (sad, I know), and was wondering if anyone knows how to do a facsimile of her costume on the cheap? I'm a (broke) student, so the cheaper the better. I'm not immensely bothered with accuracy, but I'd like it to be recognizable! I live in the UK if anyone has any cheap shop suggestions.

Thanks so much!