Indoor Hibiscus

I have a red Hibiscus in a large pot that I had on my doorstep during the summer, as of when I first bought it.
Now winter is here, I have brought it in for the protection against the frosty weather.

While on the doorstep it grew only 2 flowerheads towards late summer, of which when fully opened suddenly dropped off.
Now I have brought it in, the flowerheads which hasn't even opened completely yet, 2 still at open bud stage, are still dropping off.

Could it be our climate?

I have just read somewhere how when in a large pot they can grow atleast 6' tall. It would be such a shame to see it deteriate, as it started off well.

:confused:

 

Hibiscus is hardy, so it shouldn't have a problem outside, although I think I'd be inclined to wrap it in fleece since it's in a pot, since there isn't all that much soil to protect the roots from freezing.
http://www.bbc.co.uk/gardening/plants/plantprofile_hibiscus.shtml#recommended_varieties
Gives some info about them.