overwintering solanum rantonnettii

I bought this plant in the spring and it is in a pot.  It is in full flower and a striking deep blue colour.  I know it's not fully hardy so....should I bring it into our unheated lobby with the geraniums or would it be happy in my unheated greenhouse?  Should I cut it back now.....or in the spring (it's grown quite large).  Should I fleece it?

Thanks.