Thomson DHD4000 - Problems since digital switchover London?

I only use my Thomson PVR for recording as I have a new digital smart TV. On the initial switchover the BBC channels when viewed/recorded on the PVR were freezing and the sound was breaking up. Now since the final switchover all channels are the same. Purchased an attenuator as someone suggested the signal may now be too strong but that doesn't work either. Anyone have an easy remedy? I have just retired and I am now using my equipment more and this is most annoying, so much for the 'easy switchover'.