Help! Black Tie Dinner....

[NeedANewDress]

Hi! I have name changed as my details are a little outing and I know mum frequents this board... Hi Mum!
I was hoping you fabulous people will be able to help as I have a black tie dinner to attend and I have to have an outfit by Friday and I have no idea what to wear and/or where to buy from. I do have some lovely clothes in my wardrobe but I don't know if any of them would be suitable, so if you could offer suggestions as to what would be appropriate as well as links to items that might be available to buy I would really appreciate it, as I may already have something but I'm not sure. Not stuck on the idea of a dress, though it would be lovely, so any trouser ideas would also be greatly appreciated.
List of requirements (and this is where it gets tricky):

1. I am based in Australia so I need someone that will deliver for not eye-watering prices. (This also means that I won't be around to reply to messages during the UK day, I'll be sleeping. I will respond in my morning though)
2. The event is a black tie dinner in the middle of a work conference. The industry is very older - male dominated, over 50% of the attendees will be >50yo males.
3. I am 34 years old, 6ft tall, a size 22-24 top with size 38JJ boobs and 18 bottom
4. I NEED to wear a bra, a proper bra. With a back and straps. I am happy showing some cleavage, but it can only be some otherwise people forget I have a face.
5. Happy to show a little leg, but can't wear a mini dress due to the 6ft tall thing...
6. Budget is woeful, around 100GBP.

If you can work your magic I would be so thankful

If you have a nice glamorous black dress in your wardrobe I’d wear that and spend the £100 buying some nice statement jewellery.

I don’t like your chances of getting anything delivered by Friday in Australia. Your best bet would be to shop your closet.

A black tie dinner requires formal clothes, but not a ball gown type dress.

This dress is the kind of thing which would work, with evening shoes/a heel and a good necklace.
www.leonaedmiston.com/au/sale/garnet-2666-j-blk.html

I like Leona Edmiston because her clothes are comfortable and flexible - one of her black dresses can be day or evening friendly.

If you have a longer skirt in an evening type fabric (a bit of shine or some glitter) you could team it with a silk shirt and jewellery.

If you have wide-legged trousers you could wear them with a silk shirt (or something sequinned or a bit glitzy) and heels. Like this: m.zara.com/au/en/gathered-satin-top-p03564160.html?v1=18660727&v2=1277504

Or lean pants with a floaty top and heels, like this:
www.asos.com/au/asos-design/asos-design-knot-front-kimono-top-in-sequin/prd/11870902?clr=khaki&colourWayId=16383665&SearchQuery=sequin%20top

Since it’s a dinner and people will mostly see your top half, a plainer bottom half in a dark colour with a glamorous top and some jewellery would be fine. You probably have those pieces in your wardrobe.

My go ti for formal dinners is black pants, heels and a copper coloured taffeta evening coat. It’s easy to wear, not outrageous and means I look a bit more interesting sitting down.

Even at a black tie dinner, I’d expect most of the men will be in lounge suits, not formal black tie.