This came up on the BBC news recently:
http://news.bbc.co.uk/1/hi/scotland/tayside_and_central/7081306.stm 

Interesting that it's only been found on colliery waste, does it require something that's in the spoil to thrive or does it tolerate something that plants that might otherwise out-compete it can't cope with.

On a slightly related tack, one thing that's puzzled me for a while now is the colouration of mountain pansies. When I lived near Skipton, they tended to be purple, but with the exception of a small patch on a hillock west of Magpie mine, the ones I see in Derbyshire are yellow. The only thing I can think of which causes this colour difference is soil acidity, as I tended to see the Yorkshire ones growing on the grits and shales. Anyone got any alternative suggestions?

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Thank you for the report on Epipactis Youngiana. How very, very interesting! Epipactis is not one of the genus of which I know much. I think it may well be found that a symbiotic, fungal association is at play. The seed is miniscule and has insufficient food reserves, thus relying on the presence of a symbiotic fungus to get started. How it got there is much more interesting! Another "Mrs Willmot's Ghost"? People make the strangest introductions! I would hazard a guess that as succession progresses, if allowed, this plant may disappear.
See RHS Dictionary of Gardening. Huxley, Griffiths and Levy. I am unable to find the ISBN, it's the four volume set. Refer to this also for information on Viola lutea.
Absolute certainty in ID is important in this much manipulated genus. The Wildflower Key. Rose. Warne. ISBN. 0 7232 2419 6 notes that the flowers are sometimes blue-violet. It does not grow in more acidic conditions.
I hope this helps.