Given your spec...want to use it all year round..you sweat easily, etc...it's way too bulky and warm, logically it shouldn't be on your short list, i suspect.
It's more type of jacket somebody might use outside summer for country activities (e.g. birdwatching) that don't generate much heat. You'd roast in it, even walking up a gentle slope, even on a cool-isa day.
I suspect in summer it would be too warm even for birdwatching.
Most walkers go for a much lighter external shell, then add extra layers (such as a thin fleece) when weather gets colder. That's a far more flexible system than a one piece coat that's very warm by itself.
200 to 300 quid is a lot of dosh for a walking jacket, you could get something from any of the top walking brands for that. Best "strategy" is to find a specialist walking retailer you can get to, ask for advice, and try lots of stuff on till you find something you really like. Reputable top-end walking brands include Rab, Montane, Mountain Equipment, Paramo. And doubtless subsequent posters will add a few more.