I don’t see the point in hiring unless you plan on going to one black tie event in your entire life.
You can pick up a perfectly acceptable dinner suit brand new for not much money. Then take it to an alterations shop/tailors (if the place you bought it from won’t do it) and get the jacket/trousers tweaked so that it fits perfectly.
You’ll look FAR better in a £150 new dinner suit that fits well, compared to a hired suit that hangs off you like an old persons minge.
Buy a nice formal shirt if you don’t have one. Again, it doesn’t have to be expensive – just make sure it fits. The “whiteness” is what you are looking for here, not some greyed out hire shirt or work shirt. There are lots of options, just avoid those wings 😉 Personally, one of my favourite shirts for wearing with a DJ actually has covered buttons, it looks really clean and sharp.
Don’t worry too much about buying new shoes if you already have some clean and shiny lace-ups. However, you’ll be amazed how many people will throw on a pair of battered Churchills or loafers and think no one will notice because it’s “only shoes”.
As for the bowtie, get a proper one. You will feel immeasurably better about yourself and people who wear black tie regularly will be more likely to think that you do too 😉
Finally, a nice pocket square (which can be a bugger to fold and sit correctly, so leave enough time to sort out!).
Just my opinion mind you, which although it can’t be wrong, it might not be in accordance with STW Black Tie Policy.