Just to let you know that mine are yellowing up nicely for the winter die off now, and the ones I saw on sale at a show today were doing the same thing. The price seems to have gone up again, but they are worth it
Also mine are in pots and I just let leaf fall from my trees cover the plants then cover mine with fleece for the winter.
I know someone here on OB has them in the garden in Canada and they get down to something like -40C over there. However the guy from the nursary said that unlike here, Canada has a permenant snow cover in the winter rather than rain like us, and therefore while it's cold it's actually pretty dry under the un-melting snow and the Cyps like that.
The instruction sheet for cyps that a different nursary handed out at the same show I bought mine from, said that it was a good idea to cover them with something like ridge tiles if they were in the ground in the winter to stop the rain getting to them.
They did say that if they are in pots you have to protect the sides from the cold as they can take cold from above but not from the sides (as they would normally be down in the ground).
I'm still not sure what I'll be doing with mine. The pot it's in is very heavy but I can move it. Possibly I'll put it in the greenhouse, although I'm not sure if it will then get cold enough as I've read they need the cold. I'm planning to aim to keep that arround 5-8C as that's what the plants I'm leaving out there need for the winter.