The short answer is no, whether in Indian territory, Nepal or other places, other than during the 1952 & 1954 Royal Horticultural Society and Natural History Museum expeditions - which had shareholders in the seed collections to help fund the lengthy trips.
Without their travels, which brought a familiarity with the region's flora, their skills as photographers along with the extensive collection of botanical specimens in the Natural History Museums herbarium in London, 'Flowers of the Himalaya', which has been a standard reference work for decades, would not have been possible. And the main-stay of the museums botanical specimens are those two expeditions in the 1950s - the expeditions having primarily been mounted due to British interest in unknown, horticulturally-promising species of Primula, Meconopsis, Rhododendron plus other plants of ornamental merit which specialist gardeners wished to have access to!
There has been a long-held myth amongst the poor (and wealthy, of which there are increasing numbers) in both Indian and Nepal that every British person is a multi-millionaire and that British botanical institutions have endless funds. The reality is that travel in the Himalaya has to be funded. It just so happened that Adam Stainton did have a private income, so did not need to "sell Himalayan seed" to help meet the cost of his travels in the Himalaya but Oleg Polunin, although having the full-time income being a botany master at a top private school in the UK, still needed to raise funds. He sold shares in seed-gathering expeditions, such as one to Kashmir. Did he have permission from the Indian Government? I doubt it very much. He also funded some of his travels by leading botanical tours (as Chris Chadwell did in the 1980s, in fact he took over from an ailing Polunin as leader of such a tour in the Miyah Nullah, Lahaul in 1985 - Oleg actually died when Chris was still with the tour group). Stainton did not need to lead tours nor collect seed to sell but did gather seed for friends. Did he have permission to do so? I doubt it very much. Did they also gather botanical specimens for the herbarium of the natural history museum? Yes. Did they have permission to do so? I doubt it very much. Polunin & Stainton's guide has been invaluable. No Indian or Nepalese botanist (and neither Polunin nor Stainton were professional botanists) has ever published a book of comparable standard - most books on floras of Indian and Nepal published in those countries by their botanists are riddled with errors, omissions and misidentifications. Stainton also published a book of Nepalese forests along with a 'Supplement' to 'Flowers of the Himalaya' (which he paid for with his own money). Did they "put something back" in return for access to Himalayan flora? Definitely. But they mostly had no permission, so no doubt if they were alive today, a BBC World Service Correspondent would no doubt have written an article about them and portrayed them as villains? Were they? You decide.
Further details to follow.