Thanks rrobbo for pointing out where I was going wrong in column 1. The clashes and gaps sorted themselves out after that although a couple of clues I'm unsure of.
The waitress in 10d. I've found ..PPY in other online dictionaries but not my 1988 Chambers. Can't see it spelt ..PPIE anywhere. Have I got that wrong? Gives me a scientific unclued 3-letter answer in row 6.
I'm sure I have the right injection on Col1 - nice trap Pointer set there with the first two letters of that column - but why must it cause amusement? Is that schoolboy humour or am I missing a subtle bit of wordplay? That injection almost sounds like a TLA if you say it - another bit of cleverness by Pointer?
Thanks everyone for the hints.