You havent said what sort of receiver.
Instead of just following the "additional channels have been found" prompt where your 1,2,3,4 have probably been renumbered as 801. 802,803,804 now do a factory reset of your TV receiver. Sometimes called shipping condition. Look in the manual if you cant see the option in MENU.
For a while the signal strength from Winter Hill (Granada Region) during the switch over was less than the Welsh receivers.