Hi Eden, my first dilemma about your question is what kind of needs your coat is for? Everyday, dressy, casual, everything? What kind of weather? Do you commute by public transport or by car?
I have looked at two coats and they both suggest you like tailored items with well defined silhouette, although they are both very very different. The first one is very ladylike and dressy, probably best to have as spare but not for everyday use, especially if you're on the bus, tram or underground. However, you say it's not warm enough, so all we know is this is the silhouette you like
The second one is beautiful coat and more for everyday use, but you say it's flimsy. I think with 80% wool you'll hardly get much better fabric in terms of the composition and warmth.
This means you might consider a down coat (I strongly suggest down, not polyester fillings, the warmth is nowhere near comparable). Or, keep searching for a tailored coat, but size it in a way to be able to layer another jacket underneath. Here is Angie's blog post with advice and here is a good example of her client wearing coat over the jacket.
I think Louise's suggestion is great regarding TXMaxx, it's a treasure trove, however I'd suggest knowing what you want before you embark on the search there because it is overwhelming. Personally, If you like Hobbs and Jogsaw, I would recommend giving Debenhams a chance - I liked their own collection called just that - Collection - they always have some nice stuff in classic bordering modern cuts, which seems to be what you're after.
