31a Fuel in amour shows all such letters ---- (6) BU-ANE so BUTANE must be the answer, but why? Butane is fuel, and the last part of the clue will then read "all such letters but an E", but that's as far as I get. What's love got to do with it (as someone once said)? I see from other posts that I'm not alone in spotting 35a appears to involve a faulty anagram.
I think that's the right explanation - I also concur with the point about 35a. I was very unhappy about the quality of quite a few clues this week: however easy or difficult they are, you should surely be able to satisfy yourself beyond all reasonable doubt that you've got the right answer.
The 'butane' clue is excellent, surely! I pointed out the faulty anagram in 35a in an answer here at breakfast-time on Monday, so yes, that one was a bit dodgy.