Disappointing George, but I don't think plants from the tropics are going to thrive in near freezing temperatures.  IMHO Curry Leaf is an ingredient that I can usually omit without much impact on the dish.  I do have the benefit of growing my own plant but to me it is an underwhelming ingredient anyway, and I rarely use it except in Sri Lankan Fish curries.

Livo, my findings are that you are spot on with your comment about trying to grow tropical plants in near freezing conditions. Seeing as one plant has bounced back, I may try building a very small chamber which can be kept warm with minimal electricity from my solar PV system, for next winter. All my power comes from solar. I no longer use any mains electricity and. as a result I save a small fortune. I may also try growing plants from grocery bunches of branches and leaves. But, as you suggest, is it even worth it, if it's not a very useful ingredient?

I'm sure it has uses George, and I do occasionally use it, but I just don't come across many recipes I cook that require it.  When I do use it, I really doubt it is an essential (in my dishes anyway).  If the recipe calls for it, I'll go and pick a sprig, but it isn't that often.