I always had a Bronte jacket when I was younger. Only seem to see them for sale at shows though but probably available online now. Otherwise the outdoor shops have good brands at better prices than the horsey brands or TK Maxx is a good bet for cheap ski jackets so super warm!
I love Harry Hall - lasts for years and really does the job. I picked up a secondhand Harry Hall jacket for DD from Ebay for £5 last week. It looks like new and is really warm, it is even smart enough for school.
Yes I've got a lot of Harry Hall stuff and never been disappointed in it. I also find that their hats somehow seem to be the right shape for my head whereas some other makes just don't feel comfy. My coat is also smart enough for public use (my neighbour remarked the other day how nice it looked) when it is clean! I've just carried a torn rug along from the field so it is now totally filthy. Horses eh? Ever wonder why you bother?
Wear what you like. Harry hall are fabulous and both my dcs have them for general winter use, ( am obsessed with not having cold damp kids!) but I always feel that new tack shop clothes are too good for generally milling about at the yard in!! We wear old stuff so it doesn't matter if it gets ruined. My one and only tip though is: fleece and horsehair is a bad combination. You'll spend for evermore looking like a yeti!!
I used to have one of those checked shirts with quilted lining that I wore like a jacket for mucking out and grooming. It was great as it was warm but the hair didn't stick to it, much better than a fleece.