Hi there,
You can get dolby surround on some freeview channels / progammes / films, but as yet no dolby digital surround. If you are using a surround sound amp / receiver that has dolby pro logic II (or DTS neo-6) then the amp will de-code the stereo (or dolby surround) information into a pseudo DD track (ie greater frequency bandwith and stereo effects in the rear speakers).
If however you are using only a stereo amp (or the speakers built into the TV), then you'll only get stereo and a centre speaker wont be needed (or be able to be used).
Hope this helps,
Graham.