Undie advice for adress please?

[BobbingForPeachys]

Am wearing a dress to a formal do next month (I say formal but the relaity is everything from ballgown to old skirt, just no jeans, and preferably could the person wearing the Tikmon costume from last year get something less- erm- lion kingy LOL)

It's a silk maxi dress, with a halyter neck and triagngle shaped front (but not too triangley- more the top of than 16 year old bond girl IYSWIM).

Need to get some undies to suit, something that hauls my bum in a bit and gives serious shape to my still BF boobs without showing.

Ideas anyone?