True Christmas is, as you say a freeview channel but is not available in all areas as it depends on the channels broadcast from your local transmitter. My daughter, 3 miles away can't get it but we do.
You can check the channels you should be receiving here.
As for Movies 24, it is not currently one that Talktalk have in their packages. These can be found here.
If your transmitter does broadcast the channel I suggest you do a rescan to see if it comes in. Also check the 800 range as it may be a "reflected" channel.