After swapping hard drives back and forth the box reloaded its OS and then re-tuned the channels and......... everything seemed OK. Since then we have found one channel, Drama on freeview 20 has a poor signal showing as a blocky picture and dropping out regularly. I swapped back to an old freeview box last evening and it shows no issues with the Drama channel (or any other that I tried). I don't understand.
Rans6.....................................