My PVR has retuned (DSO)to the wrong tra...

Not a complete solution but after much fruitless fiddling through the menu I eventually found that the programmes were actually there but under different channel numbers.
I searched a long way down the LIST of channels (on remote) The BBC1 channel I want is now 800 BBC. Selecting 1 on the remote still brings up BBC Wales.
This applies to my Humax 8000T PVR - I can't comment on other makes of Freeview box.