Finished but I'm perplexed by my last clue, 20D Certainly not confirmed as most imperial (7) N-B-E-T
I assume it's noblest (= most imperial) but can't see why.
And is there a name for the sort of clue 11A is? The definition also gives you bits of the final word:
That which controls temperature by a few switches about right. (9)
That which controls temperature = definition but also
THAT + T + SOME (backwards) around R