This post may interest you. This should allow you to project your UMG in screen space to look as if it was in 3D space, providing the same effect without the need of the 3D Widget. I would also like to let you know that using the 3D Widget is more costly because its treated as Render Target, and is affected by Post-Processing / etc. It being that you’re using it for an iPhone, I may suggest this solution for that reason alone.
Peter L. Newton