Ok, @cavagirl - you got this. You're aiming for 29:30 tomorrow, not sub 30.
Here's how...
Tonight, pasta for tea. No booze! Anything you like with the pasta, but eat lots.
Tomorrow morning, get up 45 mins before your planned run. Nothing to eat, but have two cups of strong coffee. Go to the loo, then out.
Clothing wise, you want a vest and shorts, and take a couple of jelly babies with you. You'll feel more like you're doing a "race" as opposed to leggings and a T shirt. Do a v slow 5 min jog to warm up.
Then the run itself..
Don't go off too fast! You want your first mile to be no faster than 9:30.
Second mile you'll have bedded in a bit, so feel free to speed up a bit. Ditto for the first half of the 3rd mile.
Your last half mile (or last km if you like) is where it counts. Eat your jelly babies now and kick up a gear. Forget breathing, you can breathe at the end
Give it everything, all the way to the line!
Then report back. But 29:30 is doable with just those few tweaks, I promise!!