I recently bought this jacket in black and navy. The styling on the website is terrible and they both look much better on. (honestly)
They manage to be fitted but quite boxy at the same time - if you're wearing over a dress with sleeves or with a cardigan as well it's not constricted.
Baum und Pferdgarten jacket navy
Baum and Pferdgarten jacket black
I also bought from Whistles just before lockdown 2 really useful jackets to wear over dresses - one navy , one black. They're a jersey material but more formal than a cardigan and definitely jackets rather than knitwear. They're both fitted and waist length. I don't know if they still have such a thing but might be worth a look.