99% of my stalking is South of Oxford - a mix of woodland and arable.
I pretty much stalk in a pair of Fjallraven Vidda Pro trousers all year round, with either an old Cabela’s mossy oak sweatshirt on top in Summer or a Ridgeline camo smock in the Winter. I'll sometimes add a fleece waistcoat if it's a bit nippy. If it’s really cold I'll perhaps pop an old loden smock over the top.
If it's widdling down, then a pair of flecktarn Gore-tex overtrousers often come in handy, particularly if I'm in a high-seat or still hunting, topped with a Swazi tahr smock.
I do also have a bunch of Harkila kit, some Kuiu gear, several Musto jackets and a cupboard full of sundry stalking outerwear, but by and large I can't say I've ever noticed the deer really caring what I wear.
When I go out stalking with the camera I'll often wear shorts and a sludgy-brown polo shirt, which also seem to work fine.
What I do find really helps is a pair of thin camo gloves - it prevents your hands acting like warning flags to the deer.