Check out my
resources page there are a ton of links there of places that sell swimsuits by sizes.
Brastop is probably the cheapest and they have a coupon for today for 7GBP off (LUCKY).
RIANNA10 should give you 10% there and BSMAG11 is for 11% (not 100% sure if they're working but it's definitely worth a try!!!).
In terms of support and uplifte you're going to be much, much better off in a bra sized swimsuit. If you don't believe me
see this.
As for your midsection. I definitely see what you're saying and you might be better with something lower cut to show of how thing your waist is.

No ones perfect, I have a bunch of stretch marks that can be seen on my midsection but I still wear a bikini. I do get one that's high enough to cover the worst of the loose skin but that's it.