I haven't grown it, but info from the RHS says this plant is only half hardy, is best grown in an alpine house, and needs gritty, free draining but moist soil conditions, and prefers part shade. However, below is a link to the Scottish Rock Garden Club, which suggests that it's being grown outdoors - you might want to contact them for more info

http://www.srgc.org.uk/bulblog/log2004/300604/log.html

The writer of the Bulb Log, Ian Young, lives in Aberdeen and you cannot get a much more difficult climate than that outside of central North America!

Trouble is, Bulbaholic, that blog was written in 2004 - I'd be asking if the plant is still thriving if it actually is outdoors.... particularly as Oxfordshire gets some pretty low temperatures in winter compared to some areas of the UK.

From the reading of the blog, Bamboo, it sounds as if it can be a bit of a pest as he says they keep having to pulling bits out to stop it spreading. I suspect that it doesn;t exist any more but due to human intervention rather than climate!

Right, I have just asked the Youngs this question and theirs is still alive and well. There are two forms of P. communis and both look identical. The trouble is that one is from South Africa and the other from the Himalays! The Himalayan form in the Youngs garden has survived the prolonged spell of -19C a few years ago. Unless Gardenlife can find out the origin of their plant then they just hacve to take the chance. I would suggest that if it came from a garden centre then it is probably the South African form.
On the web a few hardy plant nurseries stock this for garden use. One suggests removing a few rhizomes and potting them up as an over-winter precaution, just in case!