I had some recent problems with the BBC channels on my Nokia MM9602 using DVB2000 myself. The thing is that the box apparently won't stop sending the 22 kHz signal
to the LNB despite (almost) any low band frequency (10,700 – 11,700 MHz) being entered, and therefore the box is (almost) always switched to the high band (11,700 – 12,750 MHz) and it cannot tune the low band channels.
The strange way I found out of this is to play a bit with the DiSEqC settings, i.e. change from A to either B or C (but not D). Somehow that removes the 22 kHz signal on my Nokia box and voilà the low band channels (BBC, ITV etc) reemerge (i.e. assuming you are not connected to more than one sat via a DiSEqC switch). Note that you will have to save this setting for each channel on the low band.