Thanks Stewart. I didn't think I could post any pics - when I registered there was a set of rules including one which seemed to say 'if you post photos they will be removed immediately'.
Anyway, for what they're worth, I've posted them now. I don't think it's a double flower, not like a camellia, and the petals aren't waxy at all. The flower 'buds' started off a very pale green, then turned white and looked just like single pearls before opening, directly on the stem, no stalk as such.
It's evergreen.