Meconopsis betonicifolia

Meconopsis betonicifolia, also known as Meconopsis baileyi and the Himalayan blue poppy, was first discovered in 1912, by Lt. Col. Frederick Marshman Bailey.

M. betonicifolia is hardy in most of the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and it has striking large blue flowers but it probably owes much of its success to the fact that, unlike most Meconopsis, it is perennial.