When you say "decoders" do you mean Freeview & Freesat?
We need the model number of your TV.
Why do you need to delete the FTA programmes?
All of the FTA or some in particular?
(1) Both freeview and freesat
(3)Do not need some foreign programmes ans duplicates
(4) Some programmes.
Ok, please press the SMART button on the remote control (with the house symbol) and then go to settings then setup then programme edit.
Here you can choose to delete/skip any programmes that you don't want to see.
Let me know how it goes