Thanks to everyone for your comments! And apologies for not getting back sooner!
In reality, I wrote mm 1-25 well ahead of the deadline, and wrote the rest of the work the night before. BAD PRACTICE, but I work best when I have a deadline.
I realise that this is not your regular tango. I wanted to take the hand out of it slightly, by having the main theme in 9/8 (tango 4/4 with quaver added) and make blatant and sarcastic use of the habañera rhythm.
apologies for the ending... I didn't have time to finish the piece properly!