Corsets?

I have been thinking about investing in a corset for the past six months or so. Not like a fashiony one, but a waist trainer in order to look more aesthetically pleasing and possibly enhance future cosplay costumes. So my question is.. does anyone here own a corset? And do they use it in combination with cosplay? Does it make much of a difference? And does anyone know where I can get a good corset from, preferably in the UK? I know it's like four questions in one, but anyway. :D