Are you saying that BEFORE switchover you received only the 4/5 terrestrial channels from your TV\'s analogue tuner? If so you MAY need to change your aerial - it depends where you live and which transmitter you want to tune to. If you look here and type in your postcode you should get the info you need.
http://www.ukfree.tv/txdetail.php?a=SE553962
PS don\'t forget your TV must have a digital/freeview tuner after switchover, otherwise you won\'t get anything.