Trainer corsets

[Giddypants]

I'm thinking of buying one to hold me in a it for a wedding.
Any ideas what I should be looking for.
Also, under bust or over bust? My boob to waist ratio is slightly bigger so, would be cramming my boobs into a small cup.
Or can you wear a bra with an under boob corset?

It sounds like you're not looking for a specific waist training corset, just one for occasional wear? They are different generally.

For a decent corset you want one which is steel boned - the plastic boning just buckles. Some corsets are more friendly to bigger boobs than others, for example I have one from Vollers which worked for me when I was about a 30G but doesn't work at a 30HH/J. It depends a lot on what you are wearing it with - my Vollers overbust is one which is made as outerwear rather than underwear and wouldn't work under many dresses.

I also have an underbust, which you absolutely can wear with a bra. Mine is from Orchard Corsets and is fantastic (I have the longline extra curvy one). Beware, when you sit down the corset will stop your bra moving down much so your boobs will be much higher than normal. I could genuinely rest my chin on mine when wearing either under or overbust corsets much to DH's amusement!

Yes just occasional wear, I'm not too keen on the exceptionally high boobs though, but 6 years of more or less constant breast feeding have left them a bit worse for wear and more on the fuller side. (I used to be a B now I'm an Fblush
What kind of corset do I need for just the one off occasion? And will it still reduce my waste size?

I'd still go steel boned, and wear it a little bit before hand to break it in a little. A good corset will give several inches of waist reduction. What are you planning to wear it under?

Not really sure yet, some sort of dress I imagine

Something to remember is that a corset can sometimes create a bump beneath it (unless you are very slim), especially when you sit down. They're fantastic underneath fuller skirted outfits where the skirt hides the lines of the corset so it just looks like you have a fantastic waist - think fifties shapes and such like. But, they won't look so good underneath a more fitted shape where the edges of the corset would be visible, and quite possible a bit of a bulge too!

this is the type I have - comes in lots of fabrics. It's longer than most over the hips which helps hugely with the under-bulge I mentioned above so I can wear it with a fair number of things but the skirt needs some volume for me.

Corsets are sized by waist size, you normally buy one which is about 4" smaller than your natural waist measurement in inches.