Malone - re 10d. It's an anagram of 'halts' followed by a word meaning steering apparatus, followed by the poetic term for 'ever' This gives the 'doubled up' word to be entered. The definition is a German word (but in Chambers)
Can't help with 8d, I'm afraid. It's the only one I haven't got myself.
Anyone else find the answer to 12d a bit, well, odd, considering the clue? Assuming I'm right.