Maree, have you grown many orchids before? I would take into consideration the ease of care and how often your orchid of choice needs to be watered, what kinds of temperature, etc.
With that being taken into consideration, Dendrobiums and phals are great house plants. Dendrobiums tend to like more light, like the south window you mentioned.
Both of these types of orchids are usually easily found at home/garden stores or expos rather than a more specialized orchid that you could aquire from a dealer.
Personally, I would find what I liked and then figure out how to care for it,
hopefully before I buy it
.