Tankinis with adjustable length tops are a godsend!
M & S do longer length swimsuits; you have to be quick to grab the more flattering styles though. The best styling for us would have a straight neckline but they still do them with V necks or halter necks - just the thing to make your body look even longer.
I treated myself to a stylish, £100+ American swimsuit (from Landsend) this year. It’s not one of their longer length offerings but fits sublimely.
I’ve sometimes been able to get a good length fit by going up a size, but that doesn’t always work. I find John Lewis branded clothing particularly mean on length.
For jeans the only success I’ve had has been with the “on the waist” or now the high waists from M & S. They are cheap and cheerful enough. I can usually get away with regular when they offer a choice of length, which avoids having to hack loads off the legs.
Some of the Roma fit from Per Una is good too. All others I’m constantly tugging up.
Bowden have a good selection of Tall tops and dresses, as do Next.
Landsend do a few Tall T shirts in pure cotton.
I used to worry a lot about my weight despite my size (14) until I realised that long bodies weigh more. I’m 11st 7lb now, and at 11st I’m a size 12.
Hope you find what you want, don’t give up.