It would help you get an answer if you say what you mean by "the Thomson box". Thomson are very big company with lots of products.
Having said that, ALL Freeview boxes are "Digital".
Next, when an area "goes Digital", all analogue channels are switched off not just one.
I suggest that you try a "New Installation" on your box. If that fails to find all of the channels, you may need your TV antenna (aerial) aligned or even a new one.
Vic
September 2011