Drag an imageview cross boundaries of views

Question

I have a UIImageView in the top portion of my main view.

Below this I have a horizontal UIScrollView with numerous UIImageViews contained in it.

I am trying to drag any one of the UIImageViews from the UIScrollView up onto the main UIImageView in the upper portion of the screen.

However even if I set the UIImageView being dragged to BringViewToFront it does two unexpected things?

1. I can only drag the UIImageView vertically, as soon as I stray left or right the UIScrollView beings to scroll?

2. As I drag the UIImageView up to place on the main UIImageView it slides underneath it, even though I have called BringViewToFront?

Any ideas?

Thanks