We have our wedding anniversary in London in few weeks time and would like inspiration for an outfit for dinner- not sure where yet but somewhere formal and nice, but not stuffy, maybe bankside near where we are staying. We will probably walk to wherever it is unless raining so flats essential and I don't think I want anything too glam as like a cooler not trying hard vibe- and we probably wander about a bit after dinner and look at street performers/ tourist things.
I have loads of nice 'day wear' that I would also wear for most casual evenings out - skirts/midi and maxi dresses/cullotes/ in cottons / cheesecloth/ viscose etc but nothing really nice for a special-ish occasion. Last time I got dressed up was for my 40th in December 2019 
I'm 5'6 size 16 (average to large) with a defined waist, average bust and hips and narrow shoulders so a slight pear. Heavy set thighs and ugly knees so nothing above the knee. And a bulgy lower tummy pouch thing.
Doesn't have to be a dress can be separates. Budget £100ish.
All help gratefully received 