Hi op, I’m the same height and about the same age , my go to;s are me + em and Reiss,
I recently bought these, the dress I would say is an orange red and is really flattering and elegant on, I post it as you like red, I’d happily wear it to a relaxed evening do, note me + em tend to run big, so if a 12 - 14 go for the 12.
https://www.meandem.com/conceal-reveal-lace-knit-maxi-dress-poppy-red
and also these trousers in olive, they are gorgeous on, and they have the navy in your size, a silk vest , and a contrast blazer would work well to complete the outfit.
https://www.meandem.com/velvet-man-pant-intense-olive
reiss also does some great stuff, and I find them perfect for length.
To look modern, then I’d not be doing Hobbs, sequins or knee length, as that’s very dated, instead midi dresses, wide leg trousers, skimming the body type stuff, which is excellent quality, in a lovely fabric, and well cut, usually works well.