Question
We had one of these was given to us in early June.It has been outside in our "wonderful English summer" and it still looks fantastic.Is it posibble to buy seeds and growing this in an unheated greenhouse /
Many thanks.John

Answer
John,
As far as I know there is no plant that is called a betunia, but I think that you have one of the new begonias called 'Betulia' - it is a nice plant because it forms a good shape without much pinching and blooms continually. (Some begonias need a certain number of daylight hours to bloom, but this one blooms independent of hours of daylight.) You can over-winter begonias indoors very successfully by bringing them indoors now, and keeping them in an eastern or western facing window.  Water them when dry and start to fertilize again in January. If you want to make more do so by taking cuttings of the plant in February. You might also want to put the original plant in a larger pot with fresh soil in January when the hours of daylight are increasing.

As for an unheated greenhouse, I don't know where you live so I have no idea how cold it's likely to get where you are. In general, begonias don't do well when the temps go below 40 and most of them die when it goes below freezing.
I hope this helps!
C.l.