protecting delicate plants over winter

[Cogcog]

I have a camillia which after last winter had no flowers as the flowee buds develop the previous year and the frost took them all last year. It has previously been Ok over winter as it is in a large pot which I have draged in front of the kitchen window to benefit from the heat lost through the glass.

As the first frosts have started up t'north this year I have placed a large clear plastic bag over it but wondr if that wil harm it in any way? I was going to leave it on over winter. It still has the bottom foot exposed so rain can get to the roots.

Any other ideas for frost protection which will stay put in high winds and the like and not require me to remember to watch the forecast?