Durabrand (Dual) DPVR801 does tune correct stations?

Since the digital switchover I am not able to tune my Dual DPVR801 to BBC1, BBC2 (except Wales)etc.... I have carried out the software upgrade procedure (no updates available). Auto retuning only gets me BBC1 and 2 Wales, no ch11 (Sky 3), no ch19 (Dave) although DeJa View (ch25) is present. I live within a few miles of Winter Hill and had no problem until the switchover.
When I try to manually tune to BBC1 (northwest) on number 62 I receive a note of "No Signal"
Another FreeView box on the same arial tunes all channels without any problem.
Can anyone help? Is there a fix or do I need a new box?