Black Hole
May contain traces of nut
The Tacolneston transmitter is reported to have engineering works at the moment. Maybe you should wait a week and see if it clears up.
A mains filter could be added to the amp and the Humax. Amps don't last forever, either.
Even aircraft at several thousand feet can have an effect on reception by creating multi-path distortion; that should affect all the muxes but DVB-T may be more tolerant than DVB-T2 (and should have been present generally, unless flight paths have changed or it is a combination effect).
A mains filter could be added to the amp and the Humax. Amps don't last forever, either.
Even aircraft at several thousand feet can have an effect on reception by creating multi-path distortion; that should affect all the muxes but DVB-T may be more tolerant than DVB-T2 (and should have been present generally, unless flight paths have changed or it is a combination effect).