If you were in the U.S., I'd say it's either Platanthera grandiflora (Greater Purple Fringed Orchid) or P. psycodes (Lesser Purple Fringed Orchid).
I don't know where this was growing, or its native habitat, but your photo looks similar to the North American natives named. If seen in the wild in the UK, I'd check for native orchids online.
Whatever it is, it's lovely.
Virginia
