Hi, bananabean, your penny must still be up in the air. The title is relevant – think of different possible meanings for “bit”. Yes, you have to take two letters from each of the 12 extra words to spell out the common phrase and its anagram. The letters to choose from in each word are implied by the common phrase.
This was a great relief after the unclear endgame of Listener 4422 last week, though I held myself up by misidentifying one of the words that have to be removed – I’m still convinced that it’s not needed in the clue, but it messed up the endgame. If you spot the key messages in the grid, then there’s no difficulty in resolving the answers to the eight clues that differ by one letter.