Mmm, must smell really nice in your greenhouse, Ken! Jean is right, it will probably self-pollinate.
I'd keep it in the greenhouse until your nighttime lows are at least above 40. There most likely aren't a lot of bees out and about when it's cold anyway. By the time the fruit is ripening, you'll be able to have it out in the sun to load up the fruit with sugar.
Some citrus, notably lemons, are more cold tender than others. They'll drop the flowers, and sometimes even drop leaves if they get too cold. Prolonged cold will kill them. So until you know what you've got, I'd err on the safe side and keep it warm.
