British Rhododendron ponticum (that's the commonly seen purple one) originates from Spanish and Portuguese introductions, but;

From the site 'Henning's Rhododendron history':~

In 1849 and 1850 Sir Joseph Hooker's expedition to Sikkim in the eastern Himalayas discovered forty-five new species including the yellow-flowered R. campylocarpum and R. wightii; the red-flowered R. thomsonii; the small trees, R. falconeri, R. grande, and R. hodgsonii, with their enormous leaves; the epiphytes, R. dalhousiae and R. maddenii; the large vigorous R. griffithianum with massive white flowers; and the interesting R. triflorum, R. edgeworthii, R. fulgens, R. niveum, R. wallichii, R. lanatum, R. glaucophyllum, R. cinnabarinum, and R. lepidotum. Booth found R. hookeri and R. nuttalli in Bhutan in 1852. Planchon found R. simsii in 1854.

Sikkim is just north of Darjeeling, a bit further south than the Kashmir vale, but is also part of the Himalayian range. Kashmir is closer to the Pakistan border.

LTS