We used to get channels 11,12,17,29,32 and 132 but with picture breaking up at times.
After a manual retune we cannot get these channels at all. I have retuned a few times with no success. Maybe it is to do with the transmitter?
When you say you have manually tuned do you mean you have manually initiated an automatic tune or have you done a manual tune where you input the multiplex channel numbers? I would suggest the latter and the instructions at Link to manual tuning FAQ