I feel compelled to add to the debate on the rights/wrongs of this forum, and if I get a red card, so be it. The Listener is a fiendish challenge that is intended to stretch solvers to the limit of their capabilities, therefore simply being given the answer is counter productive to that. Yes, some clues are formidable and devious (unless it's set by Sabre when it is all clues), and a nudge to re-stimulate the determination to complete rather than resort to surrender in abject frustration is a positive output that should be embraced. The longer you stick with dogged resolve the more competent you become, the more you rely on being given the answer, the lesser is the learning. So, IMHO, no answers should appear in this forum (especially if they are available elsewhere), and hints should be as subtle as possible, but helpful - i.e. no need to further frustrate someone who has probably already started pulling their hair out.
As for crossword books, I have both Listener books, and I tore out the solutions and shredded them - which has since caused me considerable anguish. If you go to the the Listener site, every puzzle set will tell you the theme of the puzzle as an incentive to continue - but NO answers are available - maybe a valuable lesson to be learned.