Decorata
 H. 'Decorata'
Dark green leaves with irregular creamy-white margins with some gray streaking into the leaf.
The RHS Plant Finder lists this as a species, h. decorata. This cultivar has also been known as Thomas Hogg in the US - confusing!

Alternative: h. 'Coquette'
Plant Size
   Medium: 15" x 42"  
Leaf
   6" x 4"; dark green, white margins  
Flower
   Pale purple with deep purple stripes  
Parentage
   unknown  
Images to follow
In the meantime check out the Hosta Library